Method for transmitting downlink control channel in a mobile communications system and a method for mapping the control channel to physical resource using block interleaver in a mobile communications system

ABSTRACT

A method for transmitting a downlink control channel in a mobile communication system and a method for mapping the control channel to physical resources using a block interleaver are provided. In order to transmit a downlink control channel in a mobile communication system, information bits are modulated to generate one or more modulation symbols according to a specific modulation scheme, the modulation symbols are interleaved using a block interleaver, and the interleaved modulated symbols are mapped to resource elements allocated for transmission of at least one control channel in a subframe, thereby transmitting the at least one control channel.

TECHNICAL FIELD

The present disclosure relates to a mobile communication system, andmore particularly, to a method for transmitting a downlink controlchannel in a mobile communication system and a method for mapping thecontrol channel to physical resources using a block interleaver.

BACKGROUND ART

In an Orthogonal Frequency Division Multiplexing (OFDM) communicationsystem, uplink/downlink data packets are transmitted in units ofsubframes, each of which is defined as a specific time intervalincluding multiple OFDM symbols. In the system, multiple terminals cancommunicate through one base station and wireless resources areallocated through scheduling of the respective terminals.Uplink/downlink communication of a terminal is performed through theresources allocated in subframes.

Here, not only uplink/downlink data packets but also various pieces ofcontrol information for transmission of the uplink/downlink data packetsare transmitted. The control information includes various pieces ofinformation required to transmit and receive uplink/downlink datapackets such as wireless resource information, coding methods, andmodulation methods used for transmitting and receiving uplink/downlinkdata packets. Resources are allocated to all or part of multiple OFDMsymbols included in one subframe for transmitting such various pieces ofcontrol information as well as for transmitting data packets. Thecontrol information is transmitted through the allocated resources inthe subframe.

According to wireless resource scheduling for transmittinguplink/downlink data packets and control information of multipleterminals, the base station maps corresponding information bits towireless resources to transmit the information bits to the terminals. Inthe case of downlink control channel transmission, mapping wirelessresources to control channels for terminals so that the control channelsare uniformly distributed and transmitted over the allocated wirelessresources advantageously achieves diversity effects since pieces ofcontrol information of a number of terminals can be transmitted togetherin downlink. In the case where scheduling is performed using virtualresource units, a method for mapping the virtual resource units toactual physical resources should be provided to perform actualtransmission.

DISCLOSURE Technical Problem

The present invention has been made in view of the above circumstancesin the background art, and it is an object of the present invention toprovide a method for transmitting downlink control channels in a mobilecommunication system. Another object of the present invention is toprovide a method for mapping control channels to physical resourcesusing a block interleaver in a mobile communication system.

Technical Solution

In accordance with one aspect of the invention, the above objects can beaccomplished by providing a method for transmitting a control channel ina mobile communication system, the method including modulatinginformation bits to generate a plurality of modulated symbols accordingto a specific modulation scheme, interleaving the plurality of modulatedsymbols using a block interleaver in units of modulated symbol groups,each including a plurality of continuous modulated symbols, mapping aplurality of modulated symbol groups to resource elements allocated fortransmission of at least one control channel in a subframe, andtransmitting the at least one control channel, wherein the interleavingincludes inputting the plurality of modulated symbol groups row by rowto the block interleaver, performing inter-column permutation on theplurality of modulated symbol groups based on a specific permutationpattern, and outputting the plurality of modulated symbol groups columnby column from the block interleaver.

The size of the block interleaver may be determined according to thenumber of the plurality of modulated symbol groups transmitted in thesubframe.

The number of rows of the block interleaver may be determined based on apredetermined number of columns of the block interleaver and the numberof the plurality of modulated symbol groups transmitted in the subframe.

Each modulated symbol group may be mapped to a resource element grouphaving a plurality of resource elements, the number of resource elementsin each resource element group being identical to the number ofmodulated symbols in each modulated symbol group.

The number of modulated symbols in each modulated symbol group and thenumber of resource elements in each resource element group may bedetermined according to the number of transmission antennas or spatialmultiplexing rate.

The plurality of modulated symbol groups may be cyclically shifted usinga cell-specific value.

The plurality of modulated symbol groups may be mapped to the resourceelements excluding resource elements allocated for at least one of areference signal, an ACK/NACK signal, and a Control Channel FormatIndicator (CCFI).

The plurality of modulated symbol groups may be mapped to the resourceelements according to a time-first mapping scheme.

The method may further include at least one of scrambling theinformation bits for the control channel prior to the modulating,mapping the plurality of modulated symbols to layers, the number ofwhich is equal to or less than the number of transmission antennas ofthe mobile communication system, and precoding the plurality ofmodulated symbols for each layer.

The control channel may be transmitted using one or more Control ChannelElements (CCEs), each including at least one of the plurality ofmodulated symbols.

Advantageous Effects

According to the embodiments described in the present disclosure, it ispossible to effectively transmit a downlink control channel in a mobilecommunication system. It is also possible to map the control channel tophysical resources using a characteristic block interleaver in themobile communication system.

In addition, according to the methods for transmitting and mappingcontrol channels described in the present disclosure, it is possible touniformly spread control information of each terminal over a totaltime/frequency domain. It is also possible to minimize the influence ofinter-cell interference in multi-cell environments through randomizationof inter-cell interference.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a procedure in which a transmitting endprocesses a signal to transmit a specific channel in a mobilecommunication system.

FIGS. 2( a) and 2(b) illustrate two examples of a method for mapping toa physical RE after performing interleaving using a block interleaveraccording to an embodiment of the invention.

FIGS. 3( a) and 3(b) illustrate detailed examples of a block interleaverapplicable to an embodiment of the invention wherein the blockinterleaver operates with different input and output directions.

FIGS. 4( a) and 4(b) illustrate how a permutation operation is performedin the method of interleaving using a block interleaver according to anembodiment of the invention.

FIGS. 5( a) and 5(b) illustrate example methods for performingintra-column permutation or intra-row permutation using a blockinterleaver according to an embodiment of the invention.

FIGS. 6( a) and 6(b) illustrate an example method for mapping a symbolsequence output from the block interleaver to physical resource elementsaccording to the embodiment of the invention.

FIG. 7 illustrates a mapping relation between virtual and physicalresources in an OFDM communication system.

FIGS. 8( a) and 8(b) illustrate example methods for determining a blockinterleaver size according to an embodiment of the invention.

FIG. 9 illustrates an example multiplexing method which can implementinterleaving using a block interleaver according to an embodiment of theinvention.

FIG. 10 illustrates a specification table provided to explain methods ofoperating a block interleaver according to an embodiment of theinvention.

FIGS. 11( a) and 11(b) illustrate a shift operation in an interleavingoperation method using a block interleaver according to an embodiment ofthe invention.

FIGS. 12( a) and 12(e) illustrate an example method for mapping acontrol channel interleaved using a block interleaver according to anembodiment of the invention.

FIGS. 13( a) to 13(d) illustrate another example method for mapping aninterleaved control channel using a block interleaver according to theembodiment of the invention.

FIG. 14 illustrates an example where a block interleaver operatesaccording to Mathematical Expression 11.

FIG. 15 illustrates an example where a block interleaver operatesaccording to Mathematical Expression 12.

FIGS. 16( a) and 16(b) illustrate a method for defining a specific groupincluding all or part of one or more CCEs according to an embodiment ofthe invention.

FIGS. 17( a) and 17(b) illustrate the method for mapping to an OFDMsymbol for transmitting a control channel using groups defined accordingto an embodiment of the invention.

FIG. 18 illustrates another method for defining a group including all orpart of one or more CCEs according to an embodiment of the invention.

FIG. 19 illustrates a method for performing mapping using a groupdefinition method according to an embodiment of the invention.

FIG. 20 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

FIG. 21 illustrates an example method using the CCE level groupingscheme according to an embodiment of the invention.

FIG. 22 illustrates another example method using the CCE level groupingscheme according to an embodiment of the invention.

FIG. 23 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

FIG. 24 illustrates an example method using the CCE sub-block levelgrouping scheme according to an embodiment of the invention.

FIG. 25 illustrates another example method using the CCE sub-block levelgrouping scheme according to an embodiment of the invention.

FIG. 26 illustrates a method for performing mapping using a groupdefinition method according to an embodiment of the invention.

FIG. 27 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

FIG. 28 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

FIG. 29 illustrates an example configuration of a block interleaver thatimplements the CCE-to-RE mapping method according to an embodiment ofthe invention.

FIGS. 30( a) and 30(b) illustrate example configurations of a blockinterleaver that implements the CCE-to-RE mapping method according to anembodiment of the invention.

FIG. 31 illustrates an example method for performing control channelmapping using a block interleaver according to an embodiment of theinvention.

FIGS. 32 and 33 illustrate, in a stepwise manner, example operations ofa block interleaver constructed according to an embodiment of theinvention.

FIG. 34 is a flow diagram sequentially illustrating CCE-to-RE mappingprocesses according to an embodiment of the invention.

FIG. 35 illustrates an example method for performing mapping afterinterleaving is done for each OFDM symbol according to an embodiment ofthe invention.

FIG. 36 illustrates an example method for transmitting different typesof control channels according to an embodiment of the invention.

FIGS. 37( a) to 37(c) illustrate an example method for allocatingmini-CCEs of a PHICH transmitted through each OFDM symbol wheninterleaving is performed on the PHICH for each OFDM symbol according toan embodiment of the invention.

FIG. 38 illustrates an example method for transmitting two or moredifferent types of control channels by performing interleaving on thedifferent types of control channels together for each OFDM symbolaccording to an embodiment of the invention.

FIG. 39 illustrates another example method for transmitting two or moredifferent types of control channels by performing interleaving on thedifferent types of control channels together for each OFDM symbolaccording to an embodiment of the invention.

FIG. 40 illustrates an example method for performing interleaving foreach OFDM symbol using a block interleaver according to an embodiment ofthe invention.

FIG. 41 illustrates an example method in which two or more controlchannels are interleaved together and are then multiplexed andtransmitted according to an embodiment of the invention.

MODE FOR INVENTION

The preferred embodiments of the present invention will now be describedin detail with reference to the accompanying drawings.

FIG. 1 illustrates an example procedure in which a transmitting endprocesses a signal to transmit a specific channel in a mobilecommunication system.

As shown in FIG. 1, the transmitting end in the mobile communicationsystem performs scrambling 10 a and 10 b for each codeword generatedafter the information bit sequence is coded. Scrambling is an operationfor mixing bits in a coded information bit sequence using an arbitraryrule (i.e., in an arbitrary order). This operation may be performedusing a specific scrambling sequence.

Modulation operations 11(a) and 11(b) are performed for the codewordsaccording to a specific modulation scheme to construct modulatedsymbols, respectively. Examples of the modulation scheme include BPSK,QPSK, 8PSK, 8QAM, 16QAM, and 64QAM. Modulated symbols generated aftermodulation can be represented by a complex number such as (x+jy).

Layer mapping (12) is performed to map the modulated symbol sequencegenerated for each codeword to layers. The number of the layers may beless than or equal to the number of transmit antennas of the mobilecommunication system and can be adaptively set, for example taking intoconsideration feedback information received from a receiving end,according to communication environments or states. Through the layermapping operation, each codeword can be mapped to one or more layers. Inthe case of a multiple antenna system, layer mapping can be performedtaking into consideration spatial multiplexing or transmit diversityeffects.

Precoding (13) can be performed after layer mapping is done. Precodingis an operation for mapping a transmission vector generated for eachlayer to resources of each transmit antenna. In the multiple antennasystem, multiple transmit antennas can be used more effectively througha specific precoding scheme.

In the case of the multiple antenna system, a variety of precodingschemes can be applied taking into consideration spatial multiplexing ortransmit diversity effects. In the case of a closed-loop system usingfeedback information from the receiving end, a codebook including aplurality of precoding matrix indices can be used to easily select aprecoding matrix used for precoding.

The modulated symbol sequences output for the transmit antennas throughprecoding in this manner are mapped to respective resource elements ofthe transmit antennas 14 a and 14 b.

The present disclosure provides a method for mapping a modulated symbolsequence for a specific channel to physical resources in a mobilecommunication system. The specific channel may include a variety oftransport channels such as a control channel that can be defined in amobile communication system. More specifically, the present disclosureprovides a method for mapping modulated symbols of a control channel tophysical resources allocated to one subframe such that resources of oneterminal can be uniformly distributed over the transmission band.

When an information bit sequence is mapped to Resource Elements (REs),basically, each RE can be directly defined as a combination of an OFDMsymbol in the time domain and a subcarrier in the frequency domain inexamples of an OFDM communication system. Mapping to REs can beperformed on the basis of a predetermined number of REs.

When mapping to REs is performed, it is possible to use the concept of aResource Block (RB) including one or more REs. An RB can be defined as acombination of multiple continuous OFDM symbols and multiple continuoussubcarriers in examples of an OFDM communication system. The size of anRB can be determined variably according to the type of a cyclic prefixor a system, a frame structure, and the like.

Besides a physical resource block which is defined as an actualtime-frequency resource, a virtual resource block, which has the samesize as a physical resource block and can be mapped to a physicalresource block, can be defined and used as a resource block. A basestation can more efficiently schedule communication resources through alogical resource concept of the virtual resource block.

For example, in this case, a specific relation is established betweenvirtual unit blocks and actual physical resource blocks, and, if thebase station schedules resources based on the virtual resource blocks,then transmission data can be mapped to actual physical resource blocksbased on the scheduling so that the transmission data can be transmittedto the receiving side through the mapped actual physical resourceblocks. It will be apparent to those skilled in the art that thephysical resource block and virtual resource block can beinterchangeably applied in the following description.

In addition, a Resource Element Group (REG) including a number of REscan be defined. Mapping of REGs can be applied in the same manner asmapping of REs. For example, when multiple antenna transmit diversitysuch as Space Frequency Block Coding (SFBC) is applied, it is possibleto take into consideration mapping to REs corresponding to the samenumber of consecutive subcarriers as the number of transmit antennasaccording to a multiple antenna transmission scheme.

In this case, one RE can be considered one REG including only onesubcarrier. Accordingly, mapping according to the above or followingembodiments can be applied to REGs, each including multiple REsaccording to the number of transmit antennas or a spatial multiplexingrate.

A modulated symbol sequence mapped to REs is converted into signals inthe time domain (for example, OFDM signals), which are then transmittedthrough respective transmit antennas.

Embodiment 1

According to this embodiment, interleaving can be performed using ablock interleaver before mapping to physical resources.

Interleaving can be performed through the block interleaver using randominterleaving or a specific permutation pattern interleaving. Due tostructural characteristics of the block interleaver, interleavingeffects can be obtained using a simple operation according to input andoutput directions (row-wise or column-wise), in which a symbol sequenceis input (written) and output (read) to and from the interleaver, andpermutation-related direction.

In addition, when outputs of the interleaver are mapped to physicalresources, a cyclic shift operation can be additionally performed usingcell-specific information such as a cell ID as a shift factor to addcell-specific elements in order to minimize inter-cell interference evenwhen the interleaver is commonly used for multiple cells.

FIGS. 2( a) and 2(b) illustrate two examples of a method for mapping toa physical RE after performing interleaving using a block interleaveraccording to an embodiment of the invention.

FIG. 2( a) illustrates an exemplary mapping method of Type 1 that isdefined as the case where the direction of input to the blockinterleaver is a row direction (row-wise).

First, at step S30, modulated symbols in the modulated symbol sequenceproduced by performing processing such as coding and modulation oninformation bits for transmission in a subframe are sequentially input(i.e., written) row-wise (i.e., row by row) to the block interleaver asassumed above. Here, it is preferable that the modulated symbols begrouped into modulated symbol groups and then the modulated symbolsequence be input in units of modulated symbol groups to theinterleaver. In the following description, it is assumed for ease ofexplanation that the modulated symbol sequence is input in units ofmodulated symbols to the interleaver and the subsequent operations areperformed in units of modulated symbols. However, it is apparent thatoperations such as a cell-specific shift operation can be applied in thesame manner to both the case of interleaving performed as describedbelow and the case of interleaving that is performed on a modulatedsymbol sequence input to the interleaver in units of modulated symbolgroups, each including a predetermined number of modulated symbols.

Then, at step S31, the block interleaver can perform interleaving suchas inter-column interleaving on modulated symbols input row-wise to theblock interleaver. For example, the block interleaver can performintra-column permutation or inter-column permutation. The intra-columnpermutation or inter-column permutation can be performed using a randompattern or a specific permutation pattern. The permutation pattern canbe generated using cell-specific information taking into considerationinter-cell interference.

Then, at step S32, shift operation can be additionally performed on themodulated symbols on which the intra-column permutation was performed atstep S32. Taking into consideration inter-cell interference,cell-specific information can be used as a shift factor for determininga shift offset.

The shift operation of step S32 can be performed in the order as shownin FIGS. 2( a) and 2(b). Alternatively, after an output process of stepS33 is performed, the shift operation can be performed on a modulatedsymbol sequence output (i.e., read) from the block interleaver so thatthe shifted symbol sequence can be mapped to physical resources. Here,after the interleaver outputs the modulated symbols at step S33,shifting may be performed using a cell-specific value, thereby reducinginter-cell interference. Of course, this operation can be removed fromthe operations of the invention.

At step S33, the block interleaver outputs the modulated symbols afterperforming random interleaving and shifting thereupon. Here, the blockinterleaver outputs symbols in a column-wise manner opposite to themanner in which they were input to the block interleaver. Then, at stepS34, the output symbol sequence is mapped to physical REs allocated forcontrol channel transmission included in a subframe and the mappedsequence is then transmitted to one or more terminals.

More specifically, interleaving is performed using a block interleaverwhich is common for multiple cells and cyclic shift is performed on themodulated symbol sequence output from the block interleaver usingcell-specific information, thereby reducing system complexity and theamount of signaling information while reducing inter-cell interference.

FIG. 2( b) illustrates an exemplary mapping method of Type 2 that isdefined as the case where the direction of input to the blockinterleaver is a column direction (column-wise).

The difference between the method of FIG. 2( b) and that of FIG. 2( a)is that the modulated symbol sequence produced by performing processingsuch as coding and modulation on information bits for transmission in asubframe is sequentially input (i.e., written) to the block interleavercolumn-wise (column by column) rather than row-wise as assumed above atstep S35, permutation is performed row by row at step S36, and themodulated symbols are output (i.e., read) row-wise (i.e., row by row)from the block interleaver at step S38. That is, detailed operations ofthe method of FIG. 2( b) are similar to those of the method of FIG. 2(a) with the only difference being input and output directions of theblock interleaver and the units in which permutation is performed.

The mapping at steps S34 and S39 in FIGS. 2( a) and 2(b) can beimplemented using a frequency (subcarrier)-first mapping scheme or atime (OFDM symbol)-first mapping scheme or a mapping scheme in which thetwo schemes are applied in units of Physical Resource Blocks (PRBs) inthe time/frequency resource regions.

The size of the block interleaver can be determined using a variety ofmethods. For example, for ease of use of the block interleaver, eitherthe row or column size of the block interleaver can be fixed and theother can be determined to be variable according to the amount ofinformation. For example, when a block interleaver is used in mappingfor control channel transmission, the column size of the blockinterleaver is fixed and the row size can be varied according to thenumber of REs or the number of modulated symbols corresponding to acontrol channel transmitted in a subframe.

On the other hand, when the determined size of the block interleaverdoes not match the number of physical REs allocated for transmission ofa specific channel in a subframe, for example, when the size of theblock interleaver is larger than the number of physical REs allocatedfor transmission of a specific channel in a subframe, the degree offreedom of the size of the block interleaver can be increased byadditionally performing processes of adding dummy elements to modulatedsymbols when the symbols are input to the block interleaver and pruningthe dummy elements when the modulated symbols are output from the blockinterleaver.

In addition, in the case where resources allocated for different channeltransmission are included in resources included in a region allocatedfor specific channel transmission in a subframe, mapping can beperformed taking into consideration the number of REs excluding theresources allocated for different channel transmission. Alternatively,mapping can be carried out by performing interleaving on a plurality ofchannels together.

For example, the number of REs, which can be used for control channeltransmission in OFDM symbols used for downlink control channeltransmission through a subframe, may exclude the number of REs used fortransmission of a Reference Signal (RS), a Physical Control FormatIndication Channel (PCFICH) carrying a Control Channel Format Indicator(CCFI) which is information regarding a control channel transportformat, a Paging Indicator Channel (PICH) or a Physical Hybrid-ARQIndicator Channel (PHICH) carrying downlink (DL) ACK/NACK, and the likein the OFDM symbols.

FIGS. 3( a) and 3(b) illustrate detailed examples of a block interleaverapplicable to an embodiment of the invention wherein the blockinterleaver operates with different input and output directions. InFIGS. 3( a) and 3(b), “R” denotes the number of rows and “C” denotes thenumber of columns.

FIG. 3( a) illustrates input and output operations of the blockinterleaver when modulated symbols are input in a row direction(row-wise) to the block interleaver. Since modulated symbols are inputrow-wise, they will be output column-wise according to the embodiment asshown in FIG. 3( a). That is, a modulated symbol sequence can be inputto the block interleaver sequentially from 1st to Rth rows of the blockinterleaver or in any order of rows. After interleaving is performed,modulated symbols can be output from the block interleaver sequentiallyfrom 1st to C columns of the block interleaver or in any order.

FIG. 3( b) illustrates input and output operations of the blockinterleaver when modulated symbols are input in a column direction(column-wise) to the block interleaver. Since modulated symbols areinput column-wise, they will be output row-wise according to theembodiment as shown in FIG. 3( a). That is, a modulated symbol sequencecan be input to the block interleaver sequentially from 1st to Cthcolumns of the block interleaver or in any order of columns. Afterinterleaving is performed, modulated symbols can be output from theblock interleaver sequentially from 1st to R rows of the blockinterleaver or in any order.

The order of elements before they are input to the block interleaver andthe order of elements that are output from the block interleaver can bechanged (or can be made different) through the simple method of usingdifferent input and output directions of the block interleaver in thismanner. Using the block interleaver with different input and outputdirections in the above manner allows channel elements to be distributedand transmitted uniformly over resources.

FIGS. 4( a) and 4(b) illustrate how a permutation operation is performedin the method of interleaving using a block interleaver according to anembodiment of the invention.

When a modulated symbol sequence is input to the block interleaver, theinter-column permutation or inter-row permutation operation according tothe embodiment can be performed by replacing all modulated symbols in arow or column in the block interleaver with those of another row orcolumn.

For example, when inter-column permutation shown in FIG. 4( a) isperformed, all modulated symbols input to the first column can bereplaced with those of another column. When inter-row permutation shownin FIG. 4( b) is performed, modulated symbols input to the first row canbe replaced with those of another row.

Inter-row permutation or inter-column permutation is an operation forchanging the order of columns or rows to be output from the interleaverbefore the interleaver outputs the modulated symbols. This operation canchange the order of columns or rows to be mapped to physical REs afterthe interleaver outputs modulated symbols.

In particular, diversity or randomness can be increased if theinter-column permutation operation is performed when the input directionis a row direction and the output direction is a column direction asshown in FIG. 4( a) and the inter-row permutation operation is performedwhen the input direction is a column direction and can be increased ifthe output direction is a row direction as shown in FIG. 4( b).

In this case, a unique permutation pattern such as a cell ID of eachcell can be generated using unique information of each cell in order tominimize the influence of inter-cell interference.

The influence of inter-cell interference can also be reduced byperforming an inter-column permutation operation using a specificpattern commonly used for each cell and an operation such as cyclicshift using a cell-specific factor.

FIGS. 5( a) and 5(b) illustrate example methods for performingintra-column permutation or intra-row permutation using a blockinterleaver according to an embodiment of the invention.

Specifically, FIG. 5( a) illustrates how intra-column permutation isperformed using a block interleaver. This method is more effective whenthe input direction of the block interleaver is a row direction.

One specific example of the method of intra-column permutation in theblock interleaver is intra-column random reordering. That is, 0^(th)column random reordering is performed on interleaver elements includedin a first column of the block interleaver and 1^(st) column randomreordering is performed on interleaver elements included in a secondcolumn of the block interleaver. In the same manner, 2^(nd) columnrandom reordering is performed on interleaver elements included in athird column of the block interleaver and c−1^(th) column randomreordering is performed on interleaver elements included in a Cth columnof the block interleaver.

The intra-column random reordering operation can be implemented byperforming a random reordering process in which row positions ofelements of each column are replaced with row positions corresponding tothe generated random numbers through random number generation orallocation. The random reordering operation can be implemented as adetailed method in which, when a random pattern for interleaving isobtained, the random pattern is stored as a lookup table in a storagemedium and the lookup table is used to smoothly perform randominterleaving and de-interleaving.

When the above intra-column random reordering operation is applied, theorder of elements of each column is determined without any regularitywith the orders of elements of other columns since, when randomreordering is applied to each column, the order of row positions ofelements of each column is individually changed based on random numbersgenerated for the column, regardless of random patterns produced byrandom reordering of elements in neighboring columns. Due to thesecharacteristics, unique mapping patterns of cells can be generated eventhough the same interleaver is used for all cells.

Mathematical Expression 1 is an example representation of theintra-column random reordering operation according to the embodiment.

(r′,c′)=(RR(r,c),c)  [MATHEMATICAL EXPRESSION 1]

In Mathematical Expression 1, r and c are variables representing row andcolumn indices of an element of the block interleaver to which aninterleaver element has been mapped or from which an interleaver elementwill be pruned before the intra-column reordering operation isperformed. r′ and c′ are variables representing row and column indicesof an element of the block interleaver to which an interleaver elementhas been mapped or from which an interleaver element will be prunedafter the intra-column reordering operation is performed.

In Mathematical Expression 1, an operation for generating a uniquereordering pattern of each column is defined as a function RR(r, c). Anyspecific operation method for generating a unique reordering pattern ofeach column can be represented by the function RR(r, c). MathematicalExpression 2 represents an example of the function RR(r, c).

RR(r,c)={r+CH(r,c)+CO(c)}% R  [MATHEMATICAL EXPRESSION 2]

In Mathematical Expression 2, a function CH(r, c) defines hopping of ablock interleaver element of a row index r (i.e., a row having index r)in a column index c (i.e., a column having index c) to an elementcorresponding to a unique value within a range of R elements in a columnvector using the two (row and column) indices. In addition, a functionCO(c) defines addition of a different offset to all elements of eachcolumn index c. A variety of operation methods can be represented usingthe function CH(r, c) and CO(c). Mathematical Expression 3 andMathematical Expression 4 represent detailed examples of the functionsCH(r, c) and CO(c) and the function RR(r, r) specified by these twofunctions.

CH(r,c)=r*c

CO(c)=c+P

RR(r,c)={r*(1+c)+e+P}% R  [MATHEMATICAL EXPRESSION 3]

CH(r,c)=r*(c+P)

CO(c)=c+P

RR(r,c)={r*(1+c+P)+c+P}% R  [MATHEMATICAL EXPRESSION 4]

In Mathematical Expressions 3 and 4, “P” represents the differencebetween an R value finally determined when the number of rows of theblock interleaver is determined to be a prime number and an R valuedetermined without taking into consideration the prime number.

When a random pattern for each column is generated, a random number maybe generated within a range having a row size of R so as to satisfy amapping requirement of the frequency domain that modulated symbols of aspecific channel of a terminal be distributed and transmitted over atotal system bandwidth and also to satisfy a mapping requirement of thetime domain that modulated symbols of a specific channel of a terminalbe transmitted uniformly using n OFDM symbols used for transmission.

If a random pattern is generated that does not satisfy theserequirements, the following problem occurs. For example, in the casewhere a control channel such as PHICH or PCFICH is transmitted through afirst OFDM symbol, the first OFDM symbol may include a CCE to which noneof the modulated symbols of a control channel for a single terminal canbe mapped according to a cell-specific shift value since the number ofREs available for PDCCH transmission in the first OFDM symbol is small.

In one method to prevent this problem, a random pattern of each columnand a random pattern of a previous column can be compared and a randomnumber distance associated with random numbers generated in each columnof a block interleaver for the modulated symbols of a specific channelof a terminal can be determined to be less than the number ofinterleaver elements that can be mapped to the first OFDM symbol. Here,the random number distance can be defined as the difference between theposition index of a specific column of a block interleaver for themodulated symbols of a control channel of a specific terminal and theposition index of a column subsequent to the specific column.

Taking into consideration the mapping requirement of the time domaindescribed above, it is possible to achieve better effects in terms oftransmission power scheduling and coverage of specific channels.

Another specific example of the method of intra-column permutation inthe block interleaver is intra-column permutation (column-wisepermutation) using a specific permutation pattern. This method can beimplemented through a specific permutation pattern based on row andcolumn indices of a resource element group that has been input to theblock interleaver. In the column-wise permutation method, it ispreferable that a permutation pattern applied to each column be uniquelyconstructed for each column. This enables implementation of intra-column(column-wise) permutation patterns with a very low correlationtherebetween.

In the case where interleaving is performed based on a specificpermutation pattern using the block interleaver as described above, thebasic operating structure is similar to that of the random interleavingof FIG. 5 with the only difference being that notations “ith-columnrandom reordering” and “ith-row random reordering” can be replaced with“ith-column-wise permutation” and “ith-row-wise permutation”. Here, “i”represents an index of each row or column when interleaving is performedrow by row or column by column.

The embodiment of the permutation pattern can be represented by thefollowing Table 1.

TABLE 1 PERMUTATION PATTERNS n = 3 (sequence length is 144) {5, 29, 50,51, 72, 88, 112, 130, 143, 15, 23, 43, 59, 82, 99, 107, 131, 147, 11,27, 40, 61, 80, 100, 110, 123, 140, 16, 26, 44, 65, 78, 95, 105, 127,145, 8, 21, 42, 66, 83, 87, 104, 120, 134, 3, 25, 45, 58, 69, 90, 103,126, 149, 9, 32, 46, 67, 79, 98, 102, 118, 136, 13, 30, 49, 53, 75, 97,114, 121, 144, 6, 17, 35, 56, 77, 101, 106, 124, 142, 1, 19, 37, 60, 74,96, 116, 128, 139, 0, 24, 38, 57, 81, 91, 109, 133, 146, 4, 28, 34, 54,76, 85, 108, 129, 135, 7, 31, 48, 62, 73, 89, 113, 119, 137, 12, 33, 47,55, 71, 92, 117, 122, 138, 2, 20, 36, 52, 70, 94, 115, 125, 141, 10, 18,39, 63, 68, 86, 111, 132, 148} n = 2 (sequence length is 72) {7, 12, 23,28, 40, 50, 52, 63, 67, 4, 15, 26, 29, 41, 46, 57, 62, 70, 8, 13, 22,30, 38, 49, 51, 66, 69, 2, 11, 19, 32, 39, 44, 54, 61, 68, 6, 10, 24,27, 42, 43, 56, 59, 71, 0, 9, 25, 31, 35,47, 58, 64, 73, 5, 17, 20, 33,36, 45, 53, 60, 74, 3, 16, 18, 34, 37, 48, 55, 65, 72}

In Table 1, numbers in “{ }” denote sequence indices of symbols in amodulated symbol sequence after interleaving, which are arranged in theorder of sequence indices of the symbols in the modulated symbolsequence before interleaving. “n” denotes the number of OFDM symbolsused for transmission of a specific channel. Here, sequence indices canbe sequentially allocated to symbols in the modulated symbol sequencebefore interleaving in the order in which the symbols are input to theinterleaver (i.e., allocated sequentially in the row direction in whichthe modulated symbols are input to the block interleaver).

Thus, the sequence indices of symbols in a modulated symbol sequencebefore interleaving can be referred to as input sequence indices. Thatis, the index of an element of 1st row and 1st column is determined tobe 0, the index of an element of 1st row and 2nd column is determined tobe 1, and the index of an element of 1st row and 3rd column isdetermined to be 2. After indices of all elements of the 1st row aredetermined, the next index can be allocated to an element of 2nd row and1st column. Remaining block interleaver elements can be sequentiallyanalyzed using the same method.

Here, sequence indices can be sequentially allocated to symbols in themodulated symbol sequence after interleaving in the order in which thesymbols are output from the interleaver (i.e., sequentially allocated inthe column direction in which the modulated symbols are output from theblock interleaver). The sequence indices of the symbols in the modulatedsymbol sequence after interleaving are denoted by numbers in Table 1.Thus, the sequence indices of symbols in the modulated symbol sequenceafter interleaving can be referred to as output sequence indices. Thatis, the index of an element of 1st row and 1st column is determined tobe 0, the index of an element of 2nd row and 1st column is determined tobe 1, and the index of an element of 3rd row and 1st column isdetermined to be 2. After indices of all elements of the 1st column aredetermined, the next index can be allocated to an element of 1st row and2nd column. Remaining block interleaver elements can be sequentiallyanalyzed using the same method.

According to the position index allocation method, Table 1 can beanalyzed as follows. When n=3, a modulated symbol at a 0th position isshifted to a 5th position after interleaving and a modulated symbol at a1st position is shifted to a 29th position after interleaving. In thiscase, two identical symbols before and after random interleaving arelocated in the same column, which indicates that intra-column randominterleaving has been performed.

FIG. 5( b) illustrates how intra-row permutation is performed using ablock interleaver. This method is more effective when the inputdirection of the block interleaver is a column direction. The method ofFIG. 5( b) can be considered the same as that of FIG. 5( a) in terms ofthe purposes and characteristics of operations of the method. However,the method of FIG. 5( b) is performed in a different random reorderingor permutation-related direction from that of FIG. 5( a).

Interleaver elements can be cyclically shifted using cell-specificinformation such as a cell ID of each cell after the block randominterleaving process is completed as described above. For example, anoutput sequence of the block interleaver for a cell having a shiftfactor of 0 can be directly mapped to physical REs without shifting andan output sequence of the block interleaver for a cell having a shiftfactor of 10 can be mapped to physical REs after cyclically shiftingelements of the sequence by 10.

The cell-specific cyclic shift operation can be performed for theentirety of an output sequence of the block interleaver. For example, aninterleaving element corresponding to the sum of a cell-specific valueand a sequence position value (for example, a sequence index) indicatinga position in the output sequence from the block interleaver can bemapped to an RE corresponding to the sequence index of the outputsequence through the cell-specific shift operation. In this case, amodulo operation using the size of the entire output sequence may beadded such that the sum of the cell-specific value and the sequenceindex does not exceed the size of the entire output sequence.

In addition, the cell-specific cyclic shift operation can be performedon the block interleaver. For example, cyclic shifting can be performedon the block interleaver column by column in the same units in whichpermutation is performed. Mathematical Expression 5 is an examplerepresentation of an intra-column random reordering operation to which acyclic shift operation of interleaver elements using cell-specificinformation (for example, cell ID) is added.

(r′,c′)=(RR(r,c)+S(Cell_ID),c)  [MATHEMATICAL EXPRESSION 5]

In Mathematical Expression 5, an operation for outputting a shift factorvalue through a cell ID is represented by a function S(Cell_ID).Mathematical Expression 6 represents an example of the functionS(Cell_ID).

S(Cell_ID,c)={Cell_ID+CO(c)}% R

CO(c)=c+P  [MATHEMATICAL EXPRESSION 6]

Mathematical Expression 6 represents an example where a different shiftfactor is generated for each column together with cell-specificinformation. This example additionally uses a function CO(c) that adds adifferent offset to all elements of each column index c described abovewith reference to Mathematical Expression 2.

Although Mathematical Expressions 5 and 6 represent examples wherecell-specific shift is performed after interleaving is done through ablock interleaver by separately using a function that outputs a shiftfactor value, a cell-specific value can also be taken into considerationwhen interleaving is performed in the above Mathematical Expressions 2to 4.

For example, it is possible to define and use a function RR(r, c,Cell_ID) by additionally taking into consideration a unique factor suchas a cell ID in a function for generating a unique reordering pattern ofeach column. Alternatively, it is possible to define and use a functionCH(r, c, Cell_ID) by additionally taking into consideration a uniquefactor such as a cell ID in a function for hopping to a unique value ineach column or to define and use a function CO(c, Cell_ID) byadditionally taking into consideration a unique factor such as a cell IDin a function for adding a different offset to all elements of eachcolumn index c.

Of course, it is possible to generate cell-specific unique mappingpatterns as described above by performing either the shift orpermutation operation. In addition, by using both the shift andpermutation operations in the interleaving operation in the mappingprocedure, it is possible to generate a larger number of cell-specificmapping patterns than when interleaving is performed using either theshift or permutation operation alone.

Mathematical Expression 7 represents an example method of representingan algorithm that can implement virtual interleaving for an interleavingoperation using the block interleaver described above.

                 [MATHEMATICAL  EXPRESSION  7] r = floor(i/C)c = i%  C $\begin{matrix}{k = {{\left\{ {{r*\left( {1 + c} \right)} + c + P} \right\} \% \mspace{14mu} R} + {(c)*R}}} \\{= {{\left\{ {{{{floor}\left( {i/C} \right)}*\left( {1 + {i\% \mspace{14mu} C}} \right)} + {i\% \mspace{14mu} C} + P} \right\} \% \mspace{14mu} R} + {\left( {i\% \mspace{14mu} C} \right)*R}}}\end{matrix}$

In Mathematical Expression 7, “r” and “c,” which can be defined as inthe above Mathematical Expression, represent position indices in theblock interleaver allocated for virtual interleaving. In addition, “i”and “k” represent the input sequence index and the output sequence indexof the block interleaver that can be seen in the description of Table 1,respectively. That is, the algorithm can be constructed using relationsbetween the input/output REG sequence indices i and k for the specificinterleaving operations of the block interleaver described above.

Here, R, C, and P may have the same values as those used when the blockinterleaver is implemented. A function floor( ) is a truncation functionwhich outputs the maximum of integer values equal to or less than aninput value.

Using the virtual interleaving method, it is possible to achieve blockinterleaving effects which can easily satisfy mapping requirements inthe time/frequency domain and minimize inter-cell interference inmulti-cell environments without additional memory or complexity.

FIGS. 6( a) and 6(b) illustrate an example method for mapping a symbolsequence output from the block interleaver to physical resource elementsaccording to the embodiment of the invention.

FIG. 6( a) represents an example where mapping is performed according toa time (OFDM symbol)-first mapping scheme. That is, in this method, thesequence of output symbols are sequentially mapped to physical resourceelements, first on the time axis, by first increasing the OFDM symbolindex in the mapping order.

FIG. 6( b) represents an example where mapping is performed according toa frequency (subcarrier)-first index mapping scheme. That is, in thismethod, the sequence of output symbols are sequentially mapped tophysical resource elements, first on the frequency axis, by firstincreasing the subcarrier symbol index in the mapping order.

An index written in each block in FIGS. 6( a) and 6(b) is an index of aspecific modulated symbol group transmitted through consecutivesubcarriers. That is, #0 can represent physical resource elements towhich modulated symbols included in a modulated symbol group 0 aremapped. In this embodiment, a single modulated symbol group includesfour modulated symbols taking into consideration that the total numberof transmit antennas is 4. From FIG. 6, it can be seen that modulatedsymbols are mapped to physical resource elements excluding those fortransmitting reference signals RS0, RS1, RS2, and RS3 for the total offour antennas.

Embodiment 2

The following embodiments will be described with reference to moredetailed examples where the block interleaving operation described aboveis performed when a base station in a mobile communication systemtransmits a downlink control channel carrying control information ofmultiple terminals, i.e., a Physical Downlink Control CHannel (PDCCH).

In the following embodiments of the invention, a control channel istransmitted using n OFDM symbols in a subframe corresponding to aTransmit Time Interval (TTI) in an OFDM communication system. Here, “n”represents the number of OFDM symbols carrying a control channel. Forexample, in a Long-Term Evolution (LTE) system, “n” can be selected fromnatural numbers equal to or less than 3 (n≦3).

Here, modulated symbols in a modulated symbol sequence of controlchannel information can be mapped to REs, respectively. For example, themodulated symbol sequence may be a sequence of symbols generated after asequence of control channel information bits undergoes all or part ofchannel coding and rate matching, cell-specific scrambling, andmodulation as described above.

A Control Channel Element (CCE), which is a virtual resource used forcontrol channel scheduling, can be defined as an element fortransmitting a control channel of a single terminal. Since the CCE is alogical resource, control information of a terminal can be actuallytransmitted through discontinuous physical resources even though thecontrol information of the terminal is transmitted through a set ofconsecutive CCEs. Relations between logical/physical resources can bepredefined in the system.

A group of modulated symbols in a CCE mapped to each REG can be definedas a mini-CCE when taking into consideration mapping to an REG includingREs corresponding to the same number of consecutive subcarriers as thenumber of transmit antennas according to a multiple antenna transmissionscheme. For example, modulated symbols in one mini-CCE can be mapped toone REG.

The sizes of a mini-CCI and an REG can be determined to correspond toeach other. Each of the sizes of a mini-CCI and an REG can be defined asincluding a variable number of modulated symbols. For example, amini-CCE can be considered a resource unit that includes a number ofmodulated symbols corresponding to the number of transmit antennas.Alternatively, a mini-CCE and an REG can each be defined as a modulatedsymbol group including a fixed number of consecutive modulated symbols.For example, a mini-CCE can be considered a resource unit including thesame number of modulated symbols as the number of subcarriers includedin a unit for application of an SFBC+FSTD technique, which combinesSpace Frequency Block Coding (SFBC) and Frequency Switched TransmitDiversity (FSTD) techniques, so that the coding technique enablingsimultaneous application of the SFBC and FSTD techniques is applied in afixed format or manner.

Here, the amount of control information that can be transmitted througha CCE can be defined according to a predefined coding rate andmodulation method. Pieces of corresponding control information can betransmitted through one or more CCEs so as to provide a terminal with acoding rate achieving a specified reception quality with a modulationmethod having been defined.

For example, control information bits transmitted through a CCE can bedefined as 48 bits when it is assumed that a CCE in a systemtransmission band includes 36 REs, the coding rate is ⅔, and the datamodulation scheme is Quadrature Phase Shift Keying (QPSK). Pieces ofcorresponding control information may be transmitted through CCEaggregation of one or more CCEs so as to provide a terminal with acoding rate achieving a specified reception quality with a modulationmethod having been defined.

Different CCEs can be defined for control information for downlink dataand control information for uplink data since the size of controlinformation for downlink data and the size of control information foruplink data may be different.

A base station performs scheduling for control channel transmission tomultiple terminals through one or more CCEs and then transmits a controlchannel by mapping the control channel to multiple REs or REGs in thephysical domain. In the following description, a process for mappingCCEs to resources in the physical domain will be referred to as “CCE toRE mapping.”

One CCE-to-RE mapping method that can be considered is distributedmapping. In this method, it is preferable that a control channel of aspecific terminal or CCEs included in the control channel be mapped tophysical REs in a distributed manner over n OFDM symbols and a totalsystem band.

In terms of the frequency domain, it is possible to obtain frequencydiversity gain by mapping CCEs to a total system band such that the CCEsare distributed over the total system band. In terms of the time domain,it is possible to increase coverage and to support balanced transmissionpower of control channels by transmitting CCEs over n OFDM symbols.

Another CCE-to-RE mapping method that can be considered is cell-specificmapping. In this method, it is preferable that CCEs be mapped tophysical REs in a cell-specific pattern (i.e., in a unique pattern foreach cell). This enables implementation of randomization of inter-cellinterference in multi-cell environments.

For example, in the case where a base station of each cell uses the sameCCE-to-RE mapping method in multi-cell environments, CCEs of each cellare mapped to the same time/frequency resource elements and thereforeinter-cell interference of transmission of CCEs may be significantlyincreased in a specific case of the method of allocation of transmissionpower of CCEs.

More specifically, it is possible to support an adaptive coding rate inorder to guarantee as uniform an error rate as possible in downlinkcontrol channels of the same type for terminals in various channelenvironments and to satisfy a preset error-rate requirement fordifferent types of downlink control channels. In the followingdescription, “CCE aggregation” actually refers to an Adaptive Modulationand Coding (AMC) level.

Transmission power control can be applied to each individual CCEaggregation level in a situation where limited CCE aggregation issupported in order to effectively maintain overhead of blind decoding ofterminals. Here, significant inter-cell interference may occur in aspecific CCE-to-RE mapping pattern in the case where the difference oftransmission power between REs of the physical domain to whichindividual CCEs are mapped is very high.

Accordingly, it is preferable that cell-specific CCE-to-RE mapping beperformed to achieve not only characteristics capable of distributingCCEs of each cell uniformly over the total time/frequency domain butalso characteristics capable of minimizing the influence of inter-cellinterference through randomization of the inter-cell interference.

Embodiment 3

FIG. 7 illustrates a mapping relation between virtual and physicalresources in an OFDM communication system.

Specifically, FIG. 7 illustrates an example where a Resource ElementGroup (REG) in an OFDM symbol is a group of k subcarriers, i.e., kResource Elements (REs), where 1≦k≦maximum number of transmit antennassupported in system.

In this case, mini-CCEs and REGs can be mapped one to one. Here, it ispreferable that mini-CCEs in one CCE be mapped to REGs in a distributedmanner through an interleaving operation using a block interleaver 600according to the invention.

A modulated symbol sequence of CCEs output from the block interleaver600 can be sequentially mapped to physical REs in the frequency or timedomain in the order from physical REs of a first OFDM symbol to those ofan nth OFDM symbol. A specific rule can also be applied when modulatedsymbols are sequentially mapped to the frequency or time domain. In thisprocess, it will be more effective to use a block interleaver withdifferent input and output directions as described above.

In this case, in the operation for mapping CCE symbols to physical REsin a specific pattern, at least one of the modulated symbols of everyCCE transmitted in a subframe in a specific bandwidth interval is mappedto physical REs. When multiple antennas are used, at least one REG maybe mapped within a specific bandwidth interval.

In addition, since a specific bandwidth interval having suchcharacteristics is mapped to the total system bandwidth, it is possibleto satisfy a mapping requirement of the frequency domain that a CCE bemapped in a distributed manner over the total system bandwidth. Inaddition, using the block interleaver described above, it is possible tosatisfy the time domain characteristics requirement that CCE symbols beuniformly mapped to each OFDM symbol according to a specific uniformitycondition.

Consequently, applying the interleaving method with different input andoutput directions achieves uniform distribution of CCEs of each cellover the total time/frequency domain in the CCE-to-RE mapping procedure.That is, optimum time/frequency diversity gain can be obtained byuniformly mapping pieces of CCE information to REs in the time/frequencydomain.

When an REG is defined, it is possible to perform mapping in units ofREGs as described above. For example, mini-CCE 0 of CCE 0 can be mappedto REG 0 and mini-CCE i+1 of CCE 1 can be mapped to REG 1.

Reference will first be made to a method of using the block interleaverdescribed above when mapping CCE to REs of the time/frequency domainaccording to a CCE-to-RE mapping method satisfying the aboverequirements and reference will then be made to a virtual interleavingmethod for virtually implementing block interleaving through setting ofrules of use of symbol memory address swapping and address arrangementof an input symbol sequence, instead of implementing block interleaveroperations through additional physical memory setting for eachoperation.

FIGS. 8( a) and 8(b) illustrate example methods for determining a blockinterleaver size according to an embodiment of the invention.

A block interleaver size according to the embodiment can be defined bythe number of rows R and the number of columns C and the R and C valuescan be determined based on not only an input CCE size but also adetailed operating method of the block interleaver.

Specifically, FIG. 8( a) illustrates an example method for determining ablock interleaver size in the case where the direction of input ofmodulated symbols to the block interleaver is a row direction. Here, thenumber of columns C of the block interleaver can be determined to be theCCE size (i.e., the number of REs or REGs to which one CCE is mapped).The number of rows R of the block interleaver can be determined to bethe maximum number of CCEs that can be transmitted in one subframe.

By constructing a block interleaver such that one CCE can be input toone row, modulated symbols of each of a plurality of CCEs in one unit oftransmission can be transmitted through distributed REs using a simpleoperation of applying different input and output directions.

By determining a column size of the block interleaver taking intoconsideration the amount of control channel information allocated to aspecific terminal and performing a permutation operation on interleaverelements in each column of the block interleaver, it is possible toguarantee the requirement that, after a CCE is mapped to physical REGs,physical REGs included in the CCE be located respectively in specificfrequency bandwidths.

By mapping mini-CCEs to REGs through an interleaving operation thatguarantees the requirement that mini-CCEs included in a CCE be locatedrespectively in specific frequency bandwidths, it is possible to map oneCCE to the total frequency bandwidth such that the CCE is uniformlydistributed over the total frequency bandwidth while preventing one CCEfrom being mapped locally to a specific frequency band.

However, since the number of REs allocated for transmission of a controlchannel in n OFDM symbols can be changed by transmission of anotherchannel, some REG may remain even when a maximum number of CCEs havebeen mapped to C REGs. In this case, the maximum number of CCEs plus 1can be determined to be the number of rows R.

More specifically, the maximum number of CCEs N_(CCE) that can betransmitted through an OFDM symbol can be defined to be

$\left\lfloor \frac{K}{C} \right\rfloor.$

In other words, R can be set to N_(CCE)+1 if K is greater than N_(CCE)*Cand R can be set to N_(CCE) if K is equal to N_(CCE)*C.

In addition, when a block interleaver operates using a specific functionto perform interleaving on each column of the block interleaver aftermodulated symbols are input in a row direction (row-wise), it may bepreferable that the number of rows R of the block interleaver be set toa prime number. If the determined R value is a prime number, it can bedirectly determined to be the number of rows R of the block interleaver.If the determined R value is not a prime number, the smallest primenumber greater than the determined R value can be determined to be thenumber of rows R of the block interleaver.

In the following, let us assume that K is the total number of REs orREGs that can be used for transmission of a control channel in n OFDMsymbols used for transmission of downlink control channels through asubframe.

If the block interleaver size is determined by the R and C valuesdetermined through the above method, mapping can be performed by pruningthe same number of elements as the difference between R*C and K. Here, KREs may include N_(CCE)*C REs used for CCE transmission and remainingK−(N_(CCE)*C) REs used for other channel transmission. The frequencydomain diversity can be optimized by determining the block interleaversize also taking into consideration K−(N_(CCE)*C) REs, which are notused for transmission of CCEs, among a total of K REs and performingblock interleaving according to the determination.

Here, the total number of K REs or REGs that can be used for controlchannel transmission may exclude the number of REs used for transmissionof a Reference Signal (RS), a Physical Control Format Indication Channel(PCFICH) carrying a Control Channel Format Indicator (CCFI) which isinformation regarding a control channel transport format, a PagingIndicator Channel (PICH) or a Physical Hybrid-ARQ Indicator Channel(PHICH) carrying downlink (DL) ACK/NACK, and the like in n OFDM symbols.

FIG. 8( b) illustrates an example method for determining a blockinterleaver size in the case where the direction of input of modulatedsymbols to the block interleaver is a column direction. Details of theimplementation method of FIG. 8( b) are similar to those of FIG. 8( a)described above with the only difference being that the number ofcolumns C of the block interleaver can be determined to be the maximumnumber of CCEs that can be transmitted in one subframe and the number ofrows R of the block interleaver can be determined to be the CCE size(i.e., the number of REs or REGs included in one CCE).

As described above, the number of rows and the number of columns of theblock interleaver are basically defined based on the maximum number ofCCEs that can be transmitted within available physical REs inassociation with CCEs which are basic scheduling units for transmissionof control channel information. However, if the total number of REsdefined based on the maximum number of transmittable CCEs is not exactlyequal to the total number of physical REs available for control channeltransmission, time/frequency domain diversity characteristics can bekept uniform by applying the pruning technique.

In summary, the number of rows or columns of the block interleaver(i.e., the size of the block interleaver) can be increased or decreasedaccording to the total number of available physical REs and the numberof rows and columns can be changed or fixed with time depending oncircumstances or conditions (or requirements).

Embodiment 4

According to this embodiment, mapping can be implemented afterinterleaving is performed using the block interleaver described abovethrough a method of multiplexing CCEs for transmitting a controlchannel.

FIG. 9 illustrates an example multiplexing method which can implementinterleaving using a block interleaver according to an embodiment of theinvention.

Specifically, FIG. 9 illustrates an example where a total of N CCEs (CCE0, CCE 1, CCE N−1) can be transmitted through one subframe and each CCEincludes a total of 9 mini-CCEs (mini-CCE 0-mini-CCE 8).

Here, a mini-CCE can be defined as an entity corresponding to a group ofmodulated symbols that are mapped to an REG according to a multipleantenna transmission technique among modulated symbols transmitted in aCCE as described above. For example, when the number of transmitantennas is 4, a modulated symbol group including a total of 4 modulatedsymbols can be defined as a mini-CCE. That is, in the followingdescription, we can assume that each mini-CCE is mapped to an REG

When mapping to an OFDM symbol is performed to transmit N CCEs, a groupof mini-CCEs is constructed such that the group of mini-CCEs includes atleast one mini-CCE of each of the N CCEs according to this embodiment.The positions of mini-CCEs are mixed through random reordering orpermutation based on a specific permutation pattern in a group ofmini-CCEs. The length of a random sequence generated through randomreordering may be limited to the maximum number of CCEs that can betransmitted in a subframe.

It is possible to perform random reordering on each group so as tosatisfy a requirement that, for each CCE, the distance between theposition of a mini-CCE of the CCE generated in a previous group and theposition of a mini-CCE of the CCE generated in a current group be lessthan the number of REGs that can be transmitted in the first OFDMsymbol.

FIG. 9 illustrates an example where a group is constructed such that itincludes at least one of the mini-CCEs of each CCE. That is, a total of9 groups including a group GO including a mini-CCE 0 of each CCE, agroup G1 including a mini-CCE 1 of each CCE, . . . , and a group G8including a mini-CCE 8 of each CCE can be formed in the example of FIG.9. The positions of REGs in each group such as group G0, group G1, . . ., and group G9 can be randomly reordered.

Here, in the case where the input direction is a row direction in themethod of using a block interleaver, it can be assumed that the numberof mini-CCEs in each group is equal to the number of rows (# of rows)and the number of groups is equal to the number of columns (# ofcolumns).

This method can be commonly applied to every cell such that randomreordering is performed for each group and a cell-specific shift of amapping pattern is performed using cell-specific information such as acell ID and mapping to physical REGs is then sequentially performed.

Embodiment 5

Reference will now be made in detail to an interleaving operation of ablock interleaver according to this embodiment which can distribute REs,to which modulated symbols of CCEs input to the block interleaver aremapped, over a total system band so as to obtain frequency diversitygain.

FIG. 10 illustrates a specification table provided to explain methods ofoperating a block interleaver according to an embodiment of theinvention.

Four types of operations shown in FIG. 10 are defined as blockinterleaving operations that are performed at a block interleaver toaccomplish purposes of CCE-to-RE mapping.

The four types can be considered extensions of the two types describedabove with reference to FIG. 2. However, while it is assumed in thedescription of FIG. 2 that an intra-column permutation or intra-rowpermutation operation and/or an inter-column permutation or inter-rowpermutation operation is performed, it is assumed in the description ofFIG. 10 that an intra-column shift or intra-row shift operation and/oran inter-column shift or inter-row shift operation is performed.

As described above, input (writing) and output (reading) directions of ablock interleaver can be set to be different in order to provide a basicdiversity gain in the time-frequency domain. As shown in FIG. 10, arow-wise writing & column-wise reading type (Type 1) and a column-wisewriting & row-wise reading type (Type 2) can be defined as two operatingtypes.

Combinations of two types of shift and permutation methods can bedefined for each of the two types of input/output methods (Type 1 andType 2). In the following description, it is assumed that thesecombinations can provide a basic diversity gain in the frequency domainand can increase coverage and support balanced transmission power ofcontrol channels in the time domain.

Two types of methods, i.e., intra-column shift & inter-columnpermutation (Method A) and intra-column shift & inter-row permutation(Method B) are associated with Type 1. Two types of methods, i.e.,intra-row shift & inter-column permutation (Method C) and intra-rowshift & inter-row permutation (Method D), are associated with Type 2.

Here, a different shift offset value or a different permutation patternmay be set for each row or each column so as to obtain effectsmaximizing diversity and randomization.

FIGS. 11( a) and 11(b) illustrates a shift operation in an interleavingoperation method using a block interleaver according to an embodiment ofthe invention. In FIGS. 11( a) and 11(b), M_(row) denotes the number ofrows and N_(col) denotes the number of columns.

The shift operation can be performed such that modulated symbolsequences of CCEs input to the block interleaver are shifted by aspecific offset value in either a row or column direction of a blockinterleaver.

For example, when an intra-column shift shown in FIG. 11( a) isperformed, the row positions of CCEs input to the same column of theblock interleaver are changed by the same offset value. In addition,when an intra-row shift shown in FIG. 11( b) is performed, the columnpositions of CCEs included in the same row of the block interleaver arechanged by the same offset value.

Especially, when the input direction of the block interleaver is a rowdirection and the output direction is a column direction, i.e., in thecase of Type 1, the intra-row shift operation is performed as shown inFIG. 11( a) and, when the input direction of the block interleaver is acolumn direction and the output direction is a row direction, i.e., inthe case of Type 2, the intra-column shift operation is performed asshown in FIG. 11( b), thereby improving diversity or randomizationcharacteristics.

Time/frequency mapping characteristics can be maintained by shiftingwithin a row or column alone taking into consideration input and outputdirections, and mapping patterns obtained after mapping is done can alsobe made various by defining a shift offset value (the extent of shift)for each row and for each column.

More specifically, cell-specific information such as a cell ID can beused to generate a shift offset value or a shift pattern based on theshift offset value in the intra-row or intra-column shift operation asdescribed above. If a shift pattern is generated using cell-specificinformation such as a cell ID, it is possible to generate a differentinterleaver output (i.e., a unique mapping pattern) for each cell eventhough an intra-column or intra-row shift operation is performed usingthe same interleaver structure for different cells as can be seen fromFIGS. 11( a) and 11(b).

Accordingly, even when an intra-column or intra-row shift operation isperformed using the same interleaver structure at a plurality of cells,cell-specific shift results can be obtained, thereby minimizing theinfluence of inter-cell interference of a control channel of each cell.

FIGS. 12( a) and 12(b) illustrate an example method for mapping acontrol channel interleaved using a block interleaver according to anembodiment of the invention.

In this embodiment, interleaving is performed using a block interleaveraccording to Type 1 & Method A (row-wise writing & column-wise reading,intra-column shift, inter-column permutation).

FIG. 12( a) illustrates a procedure in which CCEs transmitted in asubframe are input to a block interleaver in a row direction of theblock interleaver. FIG. 12( b) illustrates a method for performing anintra-column shift operation among the block interleaving operationsusing a block interleaver.

Mathematical Expression 8 represents an example of the cell-specificintra-column shift.

Q _(shift)=Cell ID % R

(r′,c′)((r+O _(shift) ·c)% R,c),  [MATHEMATICAL EXPRESSION 8]

where r=0, 1, . . . , R−1, c=0, 1, . . . , C−1

In Mathematical Expression 8, R represents the number of rows of theblock interleaver, C represents the number of columns, (r, c) representsan address of row and column before interleaving, and (r′, c′)represents an address of row and column after interleaving. And,0_(shift) represents a cell-specific factor used for a cell-specificintra-column shift operation.

If a cell-specific intra-column shift operation is performed accordingto the interleaving operation represented in FIG. 8, rows in each columnare shifted using a unique 0shift value for each cell, thereby achievinga pattern in which the positions of modulated symbols of each CCE ineach column of the block interleaver are unique for each cell.

FIG. 12( c) illustrates a method for performing an inter-columnpermutation operation among the block interleaving operations using ablock interleaver.

Mathematical Expression 9 represents an example of the cell-specificinter-column permutation.

O _(perm)=└CellID/R┘

(r′,c′)=(r,(c·P+O _(perm))% C),

where r=0, 1, . . . , R−1, c=0, 1, . . . , C−1, P=relative prime numberwith C

In Mathematical Expression 9, R represents the number of rows of theblock interleaver, C represents the number of columns, (r, c) representsan address of row and column before interleaving, and (r′, c′)represents an address of row and column after interleaving. And,0_(perm) represents a cell-specific factor used for a cell-specificinter-column permutation operation. In addition, P represents a naturalnumber relatively prime to C, which is the number of columns, and mayhave one or more values according to the value of C.

If the cell-specific inter-column permutation operation is performed,the order of columns is changed using a unique 0shift value for eachcell, so that the positions of columns is unique for each cell after theinterleaving operation is performed.

FIG. 12( d) illustrates how interleaved modulated symbols of CCEs areoutput in a column direction from a block interleaver.

As described above, block interleaver operation is not changed andinterleaving results may exhibit identical forms when input and outputdirections are changed. For example, when the input direction of theblock interleaver is changed from a column direction to a row direction,an intra-column shift operation and an inter-column permutationoperation, which are operations of the block interleaver, are replacedwith an intra-row shift operation and an inter-row permutationoperation, respectively. This indicates that the interleaving resultscan exhibit identical forms while only directions associated with theinterleaving operation have been changed.

FIG. 12( e) illustrates partial results of mapping of an interleavedsequence of modulated symbols output from a block interleaver totime/frequency resources in a subframe.

In the case where mapping is performed in units of REGs, each includingk REs, in order to support a transmit diversity technique of controlchannels, modulated symbols of CCEs are interleaved in units ofmodulated symbol groups, each including k modulated symbols, at theblock interleaver and are then mapped to REGs in units of modulatedsymbol groups.

FIGS. 13( a) to 13(d) illustrate another example method for mapping aninterleaved control channel using a block interleaver according to theembodiment of the invention.

This embodiment provides a method for performing a permutation operationor a cell-specific inter-column permutation operation at an outputprocedure rather than separately performing the operations. Embodimentsof a CCE-to-RE mapping process at each step and block interleaveroperations are described below in detail and specifically with referenceto FIGS. 13( a) to 13(d).

In this embodiment, interleaving is also performed using a blockinterleaver according to Type 1 & Method A (row-wise writing &column-wise reading, intra-column shift, inter-column permutation).

Operations of FIGS. 13( a) to 13(c) can be seen from the description ofoperations of FIGS. 12( a) to 12(c).

However, FIG. 13( c) also shows an output process. According to theexample of FIG. 13( c), modulated symbols are output in a columndirection, wherein columns can be output in any order of columns ratherthan being output sequentially starting from the first column.

FIG. 13( d) illustrates partial results of mapping of an interleavedsequence of modulated symbols output from a block interleaver totime/frequency resources in a subframe. It can be seen from FIG. 13( d)that mapping results of FIG. 13( d) are identical to those of FIG. 12(e).

In FIGS. 12( e) and 13(d), a Physical Resource Element (PRE) and aPhysical Resource Element Group (PREG) can be constructed so as toinclude k adjacent REs among REs at positions other than positions ofREs occupied by a reference signal, a PCFICH, and a PHICH among all REspresent in n OFDM symbols and a given system bandwidth.

If control channel elements are mapped to physical resource elements byperforming block interleaving as described above, it is possible tominimize inter-cell interference in multi-cell environments whilesatisfying mapping requirements in the time/frequency domain describedabove.

Although not illustrated as a detailed example, it will be apparent thatoperations of Type 1 & Method B (row-wise writing & column-wise reading,intra-column shift, inter-row permutation), Type 2 & Method C(column-wise writing & row-wise reading, intra-row shift, inter-columnpermutation), and Type 2 & Method D (column-wise writing & row-wisereading, intra-row shift, inter-row permutation) can be implemented asprocesses and methods identical to detailed interleavingoperations/configurations and processes using a block interleaver in theCCE-to-RE mapping procedure of the Type 1 & Method A scheme describedabove.

Mapping patterns generated through such processes and methods will haveunique characteristics for each cell and satisfy time/frequency domainmapping and inter-cell interference randomization characteristics as inthe case of Type 1 & Method A described in a section below.

Reference will now be made to various embodiments of determination ofcell-specific 0_(shift) values in an intra-column shift operationdescribed above in Mathematical Expression 8. First, a more generalizedintra-column shift operation can be represented by the followingMathematical Expression 10.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+v(cell_ID,cell_group_ID)+w(c))mod N_(row)  [MATHEMATICAL EXPRESSION 10]

In Mathematical Expression 10, a v(cell_ID,cell_group_ID) functionrepresents an intermediate function that can provide an RE mappingpattern index sequence adapted to each cell or each cell group using acell ID or a cell group ID. Through v(cell_group_ID), it is possible tooutput a shift offset value for coordination and randomization forcell-specific RE mapping pattern index allocation. w(c) represents anoutput function for outputting a column-based shift offset forimplementing an intra-column shift operation. Through w(c), it ispossible to generate various offset values that can be used for aspecific form of implementation of an intra-column shift operation. Oneof the v(cell_ID, cell_group_ID) and w(c) functions can be set and usedas a null function.

On the other hand, if the same offset value is applied to shift eachcolumn in the intra-column shift operation, it is possible to obtain thesame results as an inter-row permutation operation. The followingMathematical Expression 11 represents an embodiment of inter-rowpermutation for shifting a CCE group or all groups using a unique fixedoffset for each cell.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+offset(cell_ID))mod N _(row)  [MATHEMATICAL EXPRESSION11]

In Mathematical Expression 11, offset(cell_ID) represents a function forgenerating a unique shift offset for each cell using a cell ID.

FIG. 14 illustrates an example where a block interleaver operatesaccording to Mathematical Expression 11.

In the example of FIG. 14, an offset(cell_ID) value of “0” is set forcell A and an offset(cell_ID) value of “1” is set for cell B. Results ofthe inter-row permutation operation can be achieved by setting the sameshift offset value for every column of the block interleaver asdescribed above.

A specific embodiment of grouping and allocating RE mapping patterns forevery 3 cells (cell_ID=0, 1, 2) in the above embodiment can berepresented by the following Mathematical Expression 12.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+└N _(row)/3┘·cell_ID)mod N _(row)  [MATHEMATICALEXPRESSION 12]

Mathematical Expression 12 can be considered an example implementationof inter-row permutation for coordination of inter-cell interference.

FIG. 15 illustrates an example where a block interleaver operatesaccording to Mathematical Expression 12.

In the example of FIG. 15, a cell_ID value of “0” is set for cell A, acell_ID value of “1” is set for cell B, and a cell_ID value of “2” isset for cell C.

If the two above embodiments implement inter-row permutation based oncoordination of inter-cell interference, an intra-column shift operationfor allocating an offset that randomly varies for each subframe based ona cell ID and a cell group ID as an inter-row permutation operationbased on interference randomization can be represented by the followingMathematical Expression 13.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+random_(—) gen(cell_ID,cell_group_ID))mod N_(row)  [MATHEMATICAL EXPRESSION 13]

In Mathematical Expression 13, random_gen(cell_ID,cell_group_ID)represents a function for outputting a random value each time blockinterleaving is applied to a subframe and an individual REG. Thisfunction can generate a cell-specific pattern using a cell ID and a cellgroup ID.

Among embodiments of an intra-column shift operation wherein a differentoffset is applied to each column in the intra-column shift operation, anembodiment wherein shift is performed at the same intervals using anoffset of constant k for each column is represented by the followingMathematical Expression 14.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+c·k)mod N _(row)  [MATHEMATICAL EXPRESSION 14]

-   -   in case of a constant value of k

An embodiment in which a unique inter-row permutation operation for eachcell is implemented together with an intra-column shift operation in theembodiment of Mathematical Expression 14 is represented by the followingMathematical Expression 15.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+offset(cell_ID)+c·k)mod N _(row)  [MATHEMATICALEXPRESSION 15]

-   -   in case of a constant value of k

As illustrated in Mathematical Expression 15, it is possible to allocatea unique RE mapping pattern for each cell using a unique offset(cell_ID)value for each cell and a common offset(cell_ID) value of k for everycell.

Mathematical Expression 16 represents an embodiment wherein a randomvalue is generated for each column to apply a variable offset.

Input(r,c)r=0,1, . . . ,N _(row)−1

c=0,1, . . . ,N _(col)−1

Output(r′,c)r′=(r+random_(—) gen′(cell_ID,cell_group_ID))mod N_(row)  [MATHEMATICAL EXPRESSION 16]

In Mathematical Expression 16, random_gen′(cell_ID, cell_group_ID)represents a function for generating a random value for each column inorder to implement an embodiment wherein a shift offset is randomlyallocated to an RE mapping pattern for an intra-column shift operation.

Mathematical Expression 17 represents an example method of representingan algorithm for implementing virtual interleaving for an interleavingoperation using the block interleaver described above. In MathematicalExpression 17, “PREG(j)” represents j-th physical resource element.

[MATHEMATICAL EXPRESSION 17]  j = 0 For (i = 0; i<R·C; i ++) { Q = {α ·O_(perm) + (C− α)·└i/R┘} % C } Main interleaving function Temp = { ( (i% R) + R(1 + C) − O_(shift) · Q ) % R}·C + Q If (Temp < # of usefulREGs) { {close oversize brace} Address adjustment for pruning   PREG (j)= Temp   j++ }  }

In Mathematical Expression 17, R represents the number of rows ofvirtual interleaving, C represents the number of columns, (r, c)represents an address of row and column before interleaving, and (r′,c′) represents an address of row and column after interleaving. And,0_(perm) represents a cell-specific factor used for a cell-specificinter-column permutation operation and 0_(shift) represents an offsetvalue as a cell-specific factor used for a cell-specific intra-columnshift operation.

In the virtual interleaving representation, “α” used for calculation ofa Q value is a value that is variable according to C and P, where Prepresents a natural number relatively prime to C, which is the numberof columns, and may have one or more values according to the value of C.Tables 2 to 5 illustrate some combinations of the values of P and a thatcan be used according to the value of C.

TABLE 2 C = 5 P α 2 2 3 3 4 1

TABLE 3 C = 6 P α 5 1

TABLE 4 C = 9 P α 2 4 4 2 5 7 7 5 8 1

TABLE 5 C = 12 P α 5 7 7 5 11 1

If control channel elements are mapped to physical resource elementsthrough the virtual interleaving procedure as described above, it ispossible to satisfy the mapping requirements of time/frequency domainand to minimize inter-cell interference in multi-cell environments.

Embodiment 6

According to this embodiment, in the CCE-to-RE mapping proceduredescribed above, one or more groups, each including one or more CCEs,can be defined for more efficient mapping and CCEs can be mapped usingthe defined groups.

FIGS. 16( a) and 16(b) illustrate a method for defining a specific groupincluding all or part of one or more CCEs according to an embodiment ofthe invention.

FIG. 16( a) illustrates an example method in which CCEs constructed tobe transmitted in a single subframe are integrated into a singlemodulated symbol sequence and groups of arbitrary numbers of CCEs or REsare defined in the integrated modulated symbol sequence.

Specifically, FIG. 16( a) illustrates a method in which groups aredefined in units of arbitrary numbers of CCEs and modulated symbols ineach arbitrary number of CCEs are included in a corresponding group. Forexample, it can be seen from FIG. 16( a) that a total of n groups isdefined and Group #1 includes CCE#1, CCE#2, . . . , and CCE#L, Group #2includes CCE#L+1, CCE#L+2, . . . , and CCE#M, and Group #n includesCCE#M+1, CCE#M+2, . . . , and CCE#N. Here, N is the total number of CCEstransmitted in a corresponding subframe.

FIG. 16( b) illustrates a method in which groups are defined such thateach group includes one or more CCEs while modulated symbols included ina CCE can be distributed so as to be included in different groups.

Specifically, FIG. 16( b) illustrates a group definition method in whicheach CCE is divided into one or more CCE segments and a segment(s) ofevery CCE is included in one group so that modulated symbols included inone CCE are distributed so as to be included in different groups. Forexample, as shown in FIG. 16( b), a total of n groups are defined andeach CCE is divided into a number of CCE segments (for example, n CCEsegments) corresponding to the number of defined groups. CCE segment #1(S1) of each CCE is included in Group #1, CCE segment #2 (S2) of eachCCE is included in Group #2, and CCE segment #n (Sn) of each CCE isincluded in Group #n.

When one or more groups are defined using the above methods, the totalnumber of defined groups, the number of CCEs included in one group, orthe number of modulated symbols of each CCE included in one group can bedetermined in various manners. For example, these numbers can bedetermined in association with the following method for mapping to anOFDM symbol carrying a control channel using groups defined as describedbelow.

FIGS. 17( a) and 17(b) illustrate the method for mapping to an OFDMsymbol for transmitting a control channel using groups defined accordingto an embodiment of the invention.

FIG. 17( a) illustrates an example where groups are mapped respectivelyto n OFDM symbols for control channel transmission. In this case, thetotal number of defined groups may be n and the number of modulatedsymbols included in one group may be determined to be proportional to orcorrespond to the number of Physical Resource Elements (PREs), which canbe used for transmission of control information of CCEs, included in oneOFDM symbol.

As shown in FIG. 17( a), modulated symbols included in Group #1 aremapped to a first OFDM symbol in a subframe corresponding to a TransmitTime Interval (TTI), modulated symbols included in Group #2 are mappedto a second OFDM symbol, and modulated symbols included in Group #n aremapped to an nth OFDM symbol. Although groups are sequentially mapped ton OFDM symbols for control channel transmission in the exampleillustrated in FIG. 17( a), the order of mapped OFDM symbols may bechanged as needed.

FIG. 17( b) illustrates an example where one or more (for example, m)subbands, each including one or more subcarriers, are constructed in thefrequency axis for a total of n OFDM symbols for control channeltransmission. In the example illustrated in FIG. 17( b), each group ismapped to one of the m subbands. In this case, the total number ofdefined groups may be m and the number of modulated symbols included inone group may be determined to correspond to the number of PhysicalResource

Elements (PREs), which can be used for transmission of controlinformation of CCEs, included in one subband.

As shown in FIG. 17( b), modulated symbols included in Group #1 aremapped to a first subband in a subframe corresponding to a Transmit TimeInterval (TTI), modulated symbols included in Group #2 are mapped to asecond subband, and modulated symbols included in Group #m are mapped toan mth subband. Although groups are sequentially mapped to the subbandsin the example illustrated in FIG. 17( b), the order of mapped subbandsmay be changed as needed as in the example of FIG. 17( a).

PREs that can be used for transmission of control information of CCEsmay be PREs allocated for control channel transmission among all PREscorresponding to a TTI, excluding all or part of PREs for transmissionof pieces of information that are not transmitted through CCEs. Here,examples of the information not transmitted through CCEs include areference signal, a PCFICH, a PHICH, and a PICH.

In the case where all or part of REs allocated for transmission of aPCFICH, a PHICH, and a PICH, other than CCEs, and a reference signal areincluded in PREs mapped for transmission of control information of CCEs,symbol puncturing may be performed on the all or part of the REs afterCCE-to-RE mapping is terminated.

FIG. 18 illustrates another method for defining a group including all orpart of one or more CCEs according to an embodiment of the invention.

Reference will now be made to a group definition method that can beapplied when the sizes of groups, i.e., the numbers of REs included inthe groups, are different in the method described above with referenceto FIG. 16( b) wherein modulated symbols included in a CCE aredistributed so as to be included in different groups.

As shown in an upper side of FIG. 18, when each CCE is divided into oneor more CCE segments so that a CCE segment of each CCE is included inone group, the size of each CCE segment, i.e., the number of modulatedsymbols included in each CCE segment, can be determined independently ofeach other.

That is, when each group has a different size, the size of each CCEsegment can be determined to be proportional to the size of each group.For example, in the case where a total of 3 groups are defined and theratio of the sizes of the groups is 1:1:1.5, the ratio of the sizes ofCCE segments included in each CCE may be determined to be the same as1:1:1.5.

An example where each group constructed according to this embodiment ismapped to one of the total of n OFDM symbols for control channeltransmission will now be described in more detail with reference to theupper and lower sides of FIG. 18.

When modulated symbols of each CCE are transmitted by distributing themodulated symbols over n OFDM symbols, the ratio of the respectivenumbers of modulated symbols distributed to the n OFDM symbols may beequal to the ratio of the respective numbers (for example, M1:M2:M3) ofPREs that can be used for CCE transmission of the OFDM symbols. Here,when control information is transmitted through 3 OFDM symbols, thevalues of M1, M2, and M3 are numbers obtained by subtracting the numberof PREs used for other control information from M which is the number ofPREs included in each of the OFDM symbols.

The number of PREs that can be used for CCE transmission may actuallyvary for each OFDM symbol due to other control information. Accordingly,if modulated symbols of one CCE are mapped to OFDM symbols bydistributing the same number of modulated symbols over each OFDM symbolwithout taking into consideration the respective numbers of REs that canbe used for CCE transmission in the OFDM symbols, the number of CCEsthat can be transmitted in a subframe may be limited to the number ofCCEs that can be transmitted through an OFDM symbol including thelargest amount of other control information.

Each of the smallest rectangles 40 in the lower portion of FIG. 18represents a PRE and dark portions 41 represent PREs that are not usedfor actual CCE-to-RE mapping and, instead, are used for purposes otherthan CCE transmission.

An embodiment of a method (i.e., a CCE segment configuration method) inwhich modulated symbols of a CCE are divided and allocated to the OFDMsymbols such that the respective modulated symbols allocated to the OFDMsymbols are proportional to the respective numbers of PREs that can beused for CCE transmission in the OFDM symbols (for example, at a ratioof M1:M2:M3) will now be described with reference to the followingMathematical Expressions. Notations used in the following MathematicalExpressions were selected for the sake of convenience and it will beapparent that it is possible to use any other notations with the samemeanings.

The following Mathematical Expression 18 represents an example CCEsegment configuration in the case where no transmit diversity scheme isused for control channel transmission.

$\left. {{{\left. {{{\left. \mspace{355mu} {{\left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 18} \right\rbrack \mspace{20mu}\left\lbrack {{Non}\text{-}{SFBCase}} \right\rbrack}\mspace{20mu} 1} \right)\mspace{14mu} i} \neq n}{N_{RE}^{{symbol}{(i)}} = {\left\lfloor {\frac{M_{i}}{\sum\limits_{j = 1}^{n}\; M_{j}} \times {CCE}_{size}} \right\rfloor \mspace{14mu} {or}\mspace{14mu} \left\lfloor {{\frac{M_{i}}{\sum\limits_{j = 1}^{n}\; M_{j}} \times {CCE}_{size}} + 0.5} \right\rfloor \mspace{14mu} {or}\mspace{14mu} {{round}\left( {\frac{M_{i}}{\sum\limits_{j = 1}^{n}\; M_{j}} \times {CCE}_{size}} \right)}}}\mspace{20mu} 2} \right)\mspace{14mu} i} = n}\mspace{20mu} {N_{RE}^{{symbol}{(i)}} = {{CCE}_{size} - {\sum\limits_{j = 1}^{n - 1}\; N_{RE}^{{symbol}{(j)}}}}}\mspace{20mu} {{N_{CCE}^{\max}(i)} = \left\lfloor {M_{i}/\left( N_{RE}^{{symbol}{(i)}} \right)} \right)}} \right\rfloor$  N_(CCE)^(max) = min {N_(CCE)^(max)(i)}  M_(i) = availableREsforPDCCHin  i-th  OFDMsymbol  M = the  number  of  REs  in  an  OFDMsymbol  CCE_(size) = #  of  REs  in  a  CCE  N_(RE)^(symbol(i)) = the  number  of  REs  of  a  CCE  in  i-th  symbol

In Mathematical Expression 18, M denotes the number of PREs included inan OFDM symbol and M_(i) denotes the number of PREs that can be used forcontrol channel transmission in an ith OFDM symbol. Here, M_(i) can bedefined as the number of PREs other than all or part of PREs used fortransmission of other control information. CCE_(size) denotes the numberof modulated symbols included in a CCE.

In addition, N_(RE) ^(symbol(i)) is defined as the number of REs mappedto an ith OFDM symbol when REs of a CCE are transmitted in a distributedmanner over n OFDM symbols. As can be seen from Mathematical Expression18, the value of N_(RE) ^(symbol(i)) of each ith OFDM symbol may varydepending on the value of M_(i) at the OFDM symbol. The value of N_(RE)^(symbol(i)) can be determined to be proportional to a ratio between thenumber PREs that can be used for control channel transmission in n OFDMsymbols and the number PREs that can be used for control channeltransmission in the ith OFDM symbol as in the example of MathematicalExpression 18.

An operation such as flooring or rounding can be performed in order toobtain an accurate N_(RE) ^(symbol(i)) value. When the flooringoperation is used, an operation for adding 0.5 to N_(RE) ^(symbol(i))may be performed to obtain the same effects as rounding in order toprevent excessive reduction of N_(RE) ^(symbol(i)) of one OFDM symboldue to flooring.

N_(CCE) ^(max)(i) is defined as the maximum number of CCEs that cantransmit modulated symbols having a length of N_(RE) ^(symbol(i)) in anith OFDM symbol. In addition, N_(CCE) ^(max) is defined as a valuehaving the minimum value of N_(CCE) ^(max)(i) and the defined N_(CCE)^(max) may be the maximum number of CCEs that can be transmitted in onesubframe.

Using this method, the distribution of modulated symbols of a CCE foreach OFDM symbol can be adjusted so as to achieve uniform frequencydiversity gain for each OFDM symbol even in environments where thenumber of PREs that can be used for CCE transmission in each OFDM symbolvaries.

The following Mathematical Expression 19 represents an example CCEsegment configuration in the case where SFBC is used as a transmitdiversity scheme for control channel transmission. Specifically,Mathematical Expression 19 represents an example where each PRE isdefined as a pair of adjacent subcarriers in the case where a multipleantenna transmit diversity technique using two transmit antennas forcontrol channel transmission is applied. Here, the pair of adjacentsubcarriers may include two closest subcarriers among all subcarriersexcluding subcarriers to which pieces of information not transmittedthrough CCEs are mapped.

${\left. {{{\left. \mspace{11mu} {{{{\mspace{346mu} \left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 19} \right\rbrack}\mspace{20mu}\left\lbrack {{SFBC}\mspace{14mu} {case}} \right\rbrack}\text{-}{RE}\text{:}\mspace{14mu} \# \mspace{14mu} {of}\mspace{14mu} {paired}\mspace{14mu} {sub}\text{-}{carrier}}\text{}\mspace{20mu} 1} \right)\mspace{14mu} i} \neq n}{N_{RE}^{{symbol}{(i)}} = {\left\lfloor {\frac{M_{i}^{\prime}}{\sum\limits_{j = 1}^{n}\; M_{j}^{\prime}} \times {CCE}_{size}^{\prime}} \right\rfloor \mspace{14mu} {or}\mspace{14mu} \left\lfloor {{\frac{M_{i}^{\prime}}{\sum\limits_{j = 1}^{n}\; M_{j}^{\prime}} \times {CCE}_{size}^{\prime}} + 0.5} \right\rfloor \mspace{14mu} {or}\mspace{14mu} {round}\mspace{14mu} \left( {\frac{M_{i}^{\prime}}{\sum\limits_{j = 1}^{n}\; M_{j}^{\prime}} \times {CCE}_{size}^{\prime}} \right)}}\mspace{20mu} 2} \right)\mspace{14mu} i} = n$$\mspace{20mu} {N_{RE}^{{symbol}{(i)}} = {{CCE}_{size}^{\prime} - {\sum\limits_{j = 1}^{n - 1}\; N_{RE}^{{symbol}{(j)}}}}}$  N_(CCE)^(max)(i) = ⌊M_(i)^(′)/(N_(RE)^(symbol(i)))⌋  N_(CCE)^(max) = min {N_(CCE)^(max)(i)}$M_{i}^{\prime} = {{{available}\mspace{14mu} {REs}\mspace{14mu} {for}\mspace{14mu} {PDCCH}\mspace{14mu} {in}\mspace{14mu} i\text{-}{th}\mspace{14mu} {OFDM}\mspace{14mu} {symbol}} = \left\lfloor \frac{M_{i}}{2} \right\rfloor}$$\mspace{20mu} {M^{\prime} = {{{the}\mspace{14mu} {number}\mspace{14mu} {of}\mspace{14mu} {REs}\mspace{14mu} {in}\mspace{14mu} {an}\mspace{14mu} {OFDM}\mspace{14mu} {symbol}} = \left\lfloor \frac{M}{2} \right\rfloor}}$$\mspace{20mu} {{CCE}_{size}^{\prime} = {{\# \mspace{14mu} {of}\mspace{14mu} {REs}\mspace{14mu} {in}\mspace{14mu} a\mspace{14mu} {CCE}} = \left\lfloor \frac{{CCE}_{size}}{2} \right\rfloor}}$  N_(RE)^(symbol(i)) = the  number  of  REs  of  a  CCE  in  i-th  symbol

The meanings of notations defined in Mathematical Expression 19 are thesame as those of Mathematical Expression 18. However, MathematicalExpression 19 represents an example where calculation is made usingPREs, each including two subcarriers, taking into consideration SFBC.That is, taking into consideration PREs, each including two subcarriers,M, M_(i), and CCE_(size) can be redefined as M′, M′_(i), and CCE_(size)as illustrated in Mathematical Expression 2.

Mathematical Expressions 20 and 21 illustrate example calculations ofMathematical Expression 19 in the case where one CCE includes 36 REs and48 REs and three OFDM symbols are used for a control channel when thesystem transmission bandwidth is 5 MHz and 10 MHz, respectively.

${\left. {{{\left. {{\mspace{275mu} \left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 20} \right\rbrack}{Example}} \right)5\mspace{14mu} {MHz}},{4\; {Tx}\mspace{14mu} {RE}\mspace{14mu} {structure}},{SFBC}}{M^{\prime} = 150}{{M_{1}^{\prime} = 100},{M_{2}^{\prime} = 100},{M_{3}^{\prime} = 150}}{{CCE}_{size}^{\prime} = 18}{{N_{RE}^{{symbol}{(1)}} = {\left\lfloor {{\frac{100}{350} \times 18} + 0.5} \right\rfloor = 5}},{N_{RE}^{{symbol}{(2)}} = {\left\lfloor {{\frac{100}{350} \times 18} + 0.5} \right\rfloor = 5}},{N_{RE}^{{symbol}{(3)}} = {{18 - 10} = 8}}}{{{N_{CCE}^{\max}(1)} = {\left\lfloor \frac{100}{5} \right\rfloor = 20}},{{N_{CCE}^{\max}(2)} = {\left\lfloor \frac{100}{5} \right\rfloor = 20}},{{N_{CCE}^{\max}(3)} = {\left\lfloor \frac{150}{8} \right\rfloor = 18}}}{N_{CCE}^{\max} = {18\mspace{191mu}\left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 21} \right\rbrack}}{Example}} \right)10\mspace{14mu} {MHz}},{4\; {Tx}\mspace{14mu} {RE}\mspace{14mu} {structure}},{SFBC}$M^(′) = 300 M₁^(′) = 200, M₂^(′) = 200, M₃^(′) = 300 CCE_(size)^(′) = 24${N_{RE}^{{symbol}{(1)}} = {\left\lfloor {{\frac{200}{700} \times 24} + 0.5} \right\rfloor = 7}},{N_{RE}^{{symbol}{(2)}} = {\left\lfloor {{\frac{200}{700} \times 24} + 0.5} \right\rfloor = 7}},{N_{RE}^{{symbol}{(3)}} = {{24 - 14} = 10}}$${{N_{CCE}^{\max}(1)} = {\left\lfloor \frac{200}{7} \right\rfloor = 28}},{{N_{CCE}^{\max}(2)} = {\left\lfloor \frac{200}{7} \right\rfloor = 28}},{{N_{CCE}^{\max}(3)} = {\left\lfloor \frac{300}{10} \right\rfloor = 30}}$N_(CCE)^(max) = 28

FIG. 19 illustrates a method for performing mapping using a groupdefinition method according to an embodiment of the invention.

The first step (step 1) of the method can be referred to as a CCEgrouping step. At this step, N_(CCE) CCEs, each of which includesmodulated symbols constructed from a control information bit sequence tobe transmitted in each subframe, or partial CCE segments of each CCE canbe defined as one or more groups (for example, N_(GR) groups) for agiven purpose.

The second step (step 2) can be referred to as a permutation step. Atthis step, to achieve a given purpose, permutation can be performed onsequences of REs of all or each of the N_(GR) groups generated throughthe CCE grouping process of the first step.

The final, third step (step 3) can be referred to as an RE mapping step.At this step, a modulated symbol sequence permutated at the above secondstep can be mapped to one or more PREs defined according to a specificRE mapping method according to a given purpose. In the followingdescription, the method of mapping modulated symbols in CCEs to PREs inthe time-frequency domain in a physical channel is defined as an REmapping method.

An embodiment of the RE mapping method can be provided as follows. Inthe case where one or more RE-level distribution transmission schemesare selected for the purpose of achieving frequency diversity gain forPREs that are defined as combinations of OFDM symbols and subcarriers orsets of subcarriers in an OFDMA system, a specific RE mapping method formapping to specific REs to achieve the above purpose for a group(s) orall REs received from the previous step can be defined and performed atthe third step.

The above steps can be combined to design a CCE-to-RE mapping procedure.The steps of the CCE-to-RE mapping procedure may be designedindependently of each other and may also be designed in association witheach other or designed as an integrated procedure for the sake ofsimplifying and optimizing the procedure. Reference will now be made inmore detail to various embodiments that can implement the stepsdescribed above.

FIG. 20 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

This embodiment is a detailed embodiment of step 1 of FIG. 19.Descriptions of operations of steps 2 and 3 are omitted since they areidentical to those described above with reference to FIG. 19. Thisembodiment relates to an example where a method for defining groups ofmodulated symbols of CCEs constructed to be transmitted in a subframe inunits of an arbitrary number of CCEs or modulated symbols is applied atstep 1 of FIG. 19.

CCEs constructed to be transmitted in a subframe are integrated into amodulated symbol sequence at step 1-1 of FIG. 20 and the integratedmodulated symbol sequence is divided into one or more groups at step1-2. In the following description, a method of defining groups in unitsof an arbitrary number of CCEs is referred to as CCE level grouping. Inthis case, mapping to PREs defined in a time-frequency domain can beperformed at the CCE level.

The number of groups N_(GR) generated by the grouping and the size ofeach group can be equal or different depending on a given purpose andsituation. Reference will now be made to examples of a method fordetermining the number of groups N_(GR) generated by grouping and a CCEsize of each group when the CCE level grouping scheme is applied.

FIG. 21 illustrates an example method using the CCE level groupingscheme according to an embodiment of the invention.

The example of FIG. 21 is an embodiment of the CCE level groupingscheme, i.e., an embodiment of steps 1-1 and 1-2 of FIG. 20, whereingrouping is performed for each OFDM symbol in the time domain. That is,in this case, CCEs are integrated at step 1-1 and the integratedmodulated symbol sequence is divided into one or more groups at step1-2.

The number of groups (N_(GR)) generated by the grouping can bedetermined to be the number of OFDM symbols (n) and the CCE size of eachgroup can be determined to be the number of available PREs included inan OFDM symbol corresponding to each group. Here, the size of each groupcan be equal or different depending on a given purpose and situation.

FIG. 22 illustrates another example method using the CCE level groupingscheme according to an embodiment of the invention.

The example of FIG. 22 is an embodiment of the CCE level groupingscheme, i.e., an embodiment of steps 1-1 and 1-2 of FIG. 20, whereingrouping is performed for each subband including an arbitrary number ofsubcarriers in the frequency domain. That is, in this case, the numberof groups (N_(GR)) generated by grouping of an integrated RE sequence atstep 1-1 can be determined to be the number of subbands (m) and the CCEsize of each group can be determined to be the number of available PREsincluded in a subband corresponding to each group.

Each subband can be defined as a set of actual consecutive subcarriersor a set of subcarriers distributed in units of one or more subcarriersin a total system transmission band depending on the type oftransmission. In this case, it is apparent that the size of each groupcan also be equal or different depending on a given purpose andsituation.

FIG. 23 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

This embodiment is another detailed embodiment of step 1 of FIG. 19.Descriptions of operations of steps 2 and 3 are omitted since they areidentical to those described above with reference to FIG. 19. Thisembodiment relates to an example where the method for defining groups ofmodulated symbols of CCEs, such that modulated symbols included in a CCEare distributed so as to be included in different groups described abovewith reference to FIG. 2( b), is applied at step 1 of FIG. 19.

At step 1-1 of FIG. 23, an operation for dividing modulated symbolsincluded in each CCE into a number of CCE segments equal to or greaterthan the total number of groups is performed in order to distribute andmap modulated symbols of CCEs. Then, at step 1-2, one or more of thedivided CCE segments of each CCE are combined into a group. The method,in which each CCE is divided into one or more CCE segments and CCEsegments are combined into a group in this manner, is defined as a CCEsub-block level grouping scheme.

The number of groups N_(GR) generated by the grouping and the size ofeach group can be equal or different depending on a given purpose andsituation. Reference will now be made to examples of a method fordetermining the number of groups N_(GR) generated by grouping and a CCEsegment size of each group when the CCE sub-block level grouping schemeis applied.

FIG. 24 illustrates an example method using the CCE sub-block levelgrouping scheme according to an embodiment of the invention.

The example of FIG. 24 is an embodiment of the CCE sub-block levelgrouping scheme, i.e., an embodiment of steps 1-1 and 1-2 of FIG. 23,wherein grouping is performed for each OFDM symbol in the time domain.That is, in this case, CCEs are divided into segments at step 1-1 anddivided CCE segments are combined to generate one or more groups at step1-2.

The number of groups (N_(GR)) generated by the grouping can bedetermined to be the number of OFDM symbols (n) and the CCE segment sizeof each group can be determined to be the number of available PREsincluded in an OFDM symbol corresponding to each group. Here, the sizeof each group can be equal or different depending on a given purpose andsituation.

FIG. 25 illustrates another example method using the CCE sub-block levelgrouping scheme according to an embodiment of the invention.

The example of FIG. 25 is an embodiment of the CCE sub-block levelgrouping scheme, i.e., an embodiment of steps 1-1 and 1-2 of FIG. 23,wherein grouping is performed for each subband including an arbitrarynumber of subcarriers in the frequency domain. That is, in this case,the number of groups (N_(GR)) generated by grouping divided CCE segmentsat step 1-1 can be determined to be the number of subbands (m) and theCCE size of each group can be determined to be the number of availablePREs included in a subband corresponding to each group.

Each subband can be defined as a set of actual consecutive subcarriersor a set of subcarriers distributed in units of one or more subcarriersin a total system transmission band depending on the type oftransmission. In this case, it is apparent that the size of each groupcan also be equal or different depending on a given purpose andsituation.

It will also be apparent that the CCE level grouping scheme can beapplied in conjunction with the CCE sub-block grouping scheme. Forexample, groups may be defined for some CCEs by dividing each CCE intoCCE segments according to the CCE sub-block level grouping scheme andgroups may be defined for some CCEs without dividing each CCE into CCEsegments according to the CCE level grouping scheme.

The positions of modulated symbols of one or more groups generatedthrough the process of step 1 are changed in the permutation process ofstep 2 in the method of FIG. 20. In the permutation process, a singlepermutation pattern can be applied or an independent permutation patterncan be applied for each individual RE group when the permutation isperformed individually for each of the groups generated at step 1. Onthe other hand, all groups may be integrated and the permutation methodof step 2 may be performed as a single process on the integrated groups.

Especially, in the case where multi-cell environments are taken intoconsideration, if the same RE mapping method as described above isapplied to all cells, the same RE mapping method is provided for eachcell. In this situation, the influence of inter-cell interference may besignificant if the same RE mapping method is applied to each cell whenpower control of the control channel is applied and frequency-domainload of the control channel is great compared to a system transmissionband in a given cell.

One method that can be considered to overcome this problem in such asituation is to implement cell-specific permutation. Examples of thecell-specific permutation method include a method for adjustinginterference between cells by coordinating the RE mapping method of eachcell, a method for randomizing inter-cell interference by statisticallymultiplexing resources, which are commonly used by each cell in aspecific RE mapping method, in the time domain, and an inter-CCEpermutation method which spreads, when the same RE mapping method isused for each cell, the influence of inter-cell interference overmultiple CCEs to achieve channel coding gain, thereby reducing theinfluence of inter-cell interference.

In the case where inter-CCE permutation is used so that the influence ofinter-cell interference is spread over a number of CCEs while an REmapping method is commonly used for every cell in multi-cellenvironments, an advantage may be obtained in that the degree of freedomof randomization of the influence of inter-cell interference isincreased. However, in this case, there may be a problem in that uniformdistances between PREs for providing optimal diversity gain in thephysical resource domain are not maintained for PREs to which modulatedsymbols of CCEs are mapped.

FIG. 26 illustrates a method for performing mapping using a groupdefinition method according to an embodiment of the invention.

This embodiment is a detailed embodiment of step 2 of FIG. 19.Descriptions of operations of steps 1 and 3 are omitted since they areidentical to those described above with reference to FIG. 19. Thisembodiment provides an RE mapping index permutation method as a methodfor performing the permutation process. The RE mapping index permutationmethod is a permutation method in which a sequence of modulated symbolsof each arbitrary group or all groups defined at step 1 is reorderedthrough cyclic shift using a predetermined shift offset.

Specifically, a sequence of modulated symbols of each arbitrary group orall groups is reordered through cyclic shift using a cell-specific shiftoffset in order to achieve coordination or randomization of inter-cellinterference in multi-cell environments. A cell-specific RE mappingindex offset of each cell can be generated using a unique index of eachcell such as a cell ID or a cell group ID.

Here, the implementation of RE mapping index permutation through shiftwith a specific uniform-interval offset extracted by a cell ID or acombination of a cell ID and a cell group ID may be consideredimplementation for coordination of typical inter-cell interference. Themethod of performing permutation using a different random value for eachsubframe in the time domain and a random permutation pattern generatedby a cell ID or a combination of a cell ID and a cell group ID can beconsidered a method implemented for randomization of statisticalinter-cell interference.

If it is assumed that REs output from a block interleaver aresequentially mapped to PREs when the permutation operation is performedusing the block interleaver, this RE mapping index permutation methodcan be basically considered an inter-row permutation operation in theblock interleaver.

FIG. 27 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

This embodiment is a detailed embodiment of step 2 of FIG. 19.Descriptions of operations of steps 1 and 3 are omitted since they areidentical to those described above with reference to FIG. 19. Thisembodiment provides inter-CCE permutation as a method for performing thepermutation process. The inter-CCE permutation method is a permutationmethod in which a sequence of modulated symbols of each arbitrary CCE orCCE segment group or a sequence of modulated symbols of all CCEs isreordered using a specific pattern. That is, using this permutationmethod, it is possible to perform mapping to PREs according to aspecific RE mapping method while multiplexing multiple CCEs, therebyspreading interference.

Also in this case, the order of modulated symbols in a modulated symbolsequence of each arbitrary CCE or CCE segment group or a sequence ofmodulated symbols of all CCEs can be changed using a cell-specificpermutation pattern in order to spread the influence of inter-cellinterference over multiple CCEs in multi-cell environments as describedabove. In addition, a cell-specific permutation pattern of each cell canbe generated using a unique index of each cell such as a cell ID or acell group ID.

If it is assumed that REs output from a block interleaver aresequentially mapped to PREs when the permutation operation is performedusing the block interleaver, this RE mapping index permutation methodcan be basically considered an intra-column shift operation in the blockinterleaver.

FIG. 28 illustrates an example method for performing mapping using agroup definition method according to an embodiment of the invention.

This embodiment is a detailed embodiment of step 2 of FIG. 19.Descriptions of operations of steps 1 and 3 are omitted since they areidentical to those described above with reference to FIG. 19. Thisembodiment provides a method for performing a permutation process usingboth the RE mapping index permutation method and the inter-CCEpermutation method.

The method for performing a permutation process using both the REmapping index permutation method and the inter-CCE permutation methodcan be implemented by sequentially performing the RE mapping indexpermutation and the inter-CCE permutation. In addition, when thepermutation operation is performed using the block interleaver, the REmapping index permutation method and the inter-CCE permutation methodcan be freely implemented simultaneously or individually through anintra-column shift operation of the block interleaver.

As described above, the block interleaver can be used in the permutationprocess of step 3 of FIG. 19. Here, only one block interleaver can beimplemented for REs mapped to OFDM symbols in the total time domain.Alternatively, the same number of block interleavers as the number ofOFDM symbols can be provided such that one block interleaver isindividually constructed for each OFDM symbol. The number of OFDMsymbols “n” can be reported through a Control Channel Format Indicator(CCFI) or cat. 0. In this case, the size of each of the n blockinterleavers may be equal to N_(RE) ^(symbol(i))×N_(CCE) ^(max)(i).

FIG. 29 illustrates an example configuration of a block interleaver thatimplements the CCE-to-RE mapping method according to an embodiment ofthe invention.

From the configuration of the block interleaver shown in FIG. 29, it canbe seen that the size of each of the n block interleavers may be equalto N_(RE) ^(symbol(i))×N_(CCE) ^(max)(i). N_(RE) ^(symbol(i)) of each ofthe N_(CCE) ^(max)(i) CCEs to be mapped to an ith OFDM symbol is inputto the block interleaver in a row direction of the block interleaver.After undergoing a series of operations, REs can be sequentially outputin a column direction so that the output REs are mapped to PREs of acorresponding physical resource domain according to the RE mappingmethod and are then transmitted through the mapped PREs.

As shown in FIG. 29, CCE(0) is input to the first row of the blockinterleaver of the ith OFDM symbol. Then, CCE(0) is input to the secondrow, CCE(1) is input to the third row, and CCE(N_(CCE) ^(max)(i)−1) isinput to the N_(CCE) ^(max)(i)th row.

FIG. 30 illustrates an example configuration of a block interleaver thatimplements the CCE-to-RE mapping method according to an embodiment ofthe invention.

A group can be constructed from CCEs for each OFDM symbol. In the casewhere a method for specifying and allocating the number of REs of eachCCE for an OFDM symbol is used, the number of PREs remaining for eachOFDM symbol may exceed the number of REs of the CCE. In this case, theexcess PREs can be allocated for transmission of an additional CCE.

Mathematical Expression 22 represents a method applied when the numberof PREs remaining for each OFDM symbol exceeds the number of REs in aCCE. To implement this method, N_(CCE) ^(max) is defined as a minimumvalue of N_(CCE) ^(max)(i) for each OFDM symbol.

                [MATHEMATICAL  EXPRESSION  22]Q(i) = #  of  residual  REs  in  i-th  OFDM  symbolQ(i) = M_(i) − (N_(CCE)^(max) ⋅ N_(Re)^(symbol(i)))Q^(′)(i) = M_(i) − (N_(CCE)^(max)(i) ⋅ N_(Re)^(symbol(i)))${{if}\mspace{14mu} {\sum\limits_{i = 1}^{n}\; {Q(i)}}} > {CCE}_{size}$$l = \left\lfloor \frac{\sum\limits_{i = 1}^{n}\; {Q(i)}}{{CCE}_{size}} \right\rfloor$if  Q^(′)(i) > 0  k(i) = N_(CCE)^(max)(i) − N_(CCE)^(max) + 1else  k(i) = N_(CCE)^(max)(i) − N_(CCE)^(max) k = max {k(i)}

Here, PREs, which are not used for transmitting modulated symbols ofCCEs for each OFDM symbol, are generated. The number of PREs which arenot used for CCE transmission for each OFDM symbol can be defined asQ(i) and Mathematical Expressions 18 and 19 can be referred to for othernotations.

If the sum of Q(i) in a subframe is greater than CCE_(size) when CCEsare transmitted using n OFDM symbols in the subframe, it is possible totransmit a larger number of CCEs than N_(CCE) ^(max). Accordingly, thenumber of OFDM symbols used for CCE transmission in the subframe is n ascan be seen from Mathematical Expression 22. Here, l and k(i) aredefined when the sum of Q(i) of the n OFDM symbols is greater thanCCE_(size).

When the sum of Q(i) of the n OFDM symbols is greater than CCE_(size), lis the number of CCEs that can be transmitted in addition to N_(CCE)^(max) CCEs in the subframe. When block interleavers constructedrespectively for the OFDM symbols are used, k(i) is the number of rowsin an interleaver of an ith OFDM symbol, which are used for transmittingl more CCEs other than N_(CCE) ^(max) CCEs, other than N_(CCE) ^(max)rows in the interleaver of the ith OFDM symbol.

Even when l rows are added for transmitting l more CCEs other thanN_(CCE) ^(max) CCEs, the number of used PREs may be insufficient forM_(i). Q′(i) is defined to use all PREs remaining in this case. Q′(i)represents a smaller number of PREs than N_(Re) ^(symbol(i)) OFDMsymbol.

FIG. 30( a) illustrates an example configuration of an interleaver of anith OFDM symbol when Q(t) and Q′(i) are taken into consideration andFIG. 30( b) illustrates an example configuration of respectiveinterleavers of n OFDM symbols when Q(i) and Q′(i) are taken intoconsideration.

Using the block interleaver constructed according to Q(i), Q′(i), l, andk(i) can reduce the number of PREs that are not used for CCEtransmission in each OFDM symbol. Through puncturing, mapping to PREsmay not performed for columns in a k(i)th row whose column indices aregreater than the length of Q′(i) when Q′(i) is greater than 0.

As shown in FIGS. 30( a) and 30(b), the same number of k rows as themaximum of k(i) of n OFDM symbols used for CCE transmission can be addedto N_(CCE) ^(max) rows to transmit l more CCEs. When this method isemployed, the input and output of the interleaver can be estimated basedon indices of the interleaver. Therefore, when k rows are added for oneOFDM symbol so that the number of modulated symbols in the CCE exceedsM_(i), mapping to PREs may not be performed by carrying out puncturingbased on the indices.

When the method employing the permutation process of step 2 through theblock interleaver is applied, the various types of intra-column shiftoperations described above can be defined as representative functionswhich are expressed by the following Mathematical Expression 23.

Input(r,c)r=0,1, . . . ,N _(CCE) ^(max)(i)−1

c=0,1, . . . ,N _(RE) ^(symbol(i))−1

Output(r′,c)r′=(r+v(cell_ID,cell_group_ID)+w(c))mod N _(CCE)^(max)(i)  [MATHEMATICAL EXPRESSION 23]

Mathematical Expression 23 represents an example of generalization of afunction v(cell_ID, cell_group_ID) that represents coordination andrandomization for allocating a cell-specific RE mapping scheme and ageneral function w(c) for various types of implementation of inter-CCEpermutation.

In Mathematical Expression 23, v(cell_ID, cell_group_ID) is ageneralized representation of a function that intermediates anintra-column shift operation that can generate a unique RE mappingscheme for each cell or each cell group based on cell_ID andcell_group_ID. And, w(c) is a generalized representation of a functionfor generating various offsets that can be used for inter-CCEpermutation.

When inter-CCE permutation is implemented using an intra-column shiftoperation, only the v(cell_ID, cell_group_ID) function may be used andonly the w(c) function may also be used and both the functions or noneof the functions may also be used in the following generalizedequations.

A description of the present embodiments will be described withreference to an example where a method of mapping each group generatedaccording to a CCE-level grouping method to each subband is applied inthe CCE grouping process of step 1 in the implementation of CCE-to-REmapping described above and an RE mapping index permutation method isapplied in the permutation process of step 2. Particularly, thedescription will be given with reference to the case where a blockinterleaver is used.

Coordination and randomization of inter-cell interference can beperformed using a block interleaver in order to reduce the influence ofinter-cell interference in the case where no inter-CCE permutation istaken into consideration.

FIG. 31 illustrates an example method for performing control channelmapping using a block interleaver according to an embodiment of theinvention.

Frequency diversity can be obtained in units of resource blocks, eachincluding an arbitrary number of PREs, in the time-frequency domain indistributed time-frequency resource conditions of an OFDM communicationsystem. In this case, resource blocks can be considered units of OFDMsymbols and can also be considered subband units, each including apredetermined number of subcarriers as described above.

In FIG. 31, N_(bit) ^(RB) is the number of CCEs per resource block andN_(RB) is the total number of resource blocks used for control channelsin the system. And, N_(RB) ^(Gr) is the number of resource blocks usedfor a group of N_(CCE) ^(Gr) CCEs.

It may be necessary to perform mapping through individual blockinterleaving for each OFDM symbol in the case where the number ofavailable Physical Resource Elements (PREs) is not uniform for each OFDMsymbol. In this case, N_(bit) ^(RB) and N_(RB) (and N_(RB) ^(Gr) asneeded) can be applied as values in an OFDM symbol.

N_(ant) subcarriers are defined as one RE when N_(ant) transmit antennasare used for SFBC employing a multiple antenna transmit diversityscheme. In the case where mapping is performed in an RE-leveldistributed transmission mode in a resource block level when N_(ant)transmit antennas are used, the value of N_(bit) ^(RB) is equal toN_(ant), N_(RB) ^(Gr) is defined as the product of N_(CCE) ^(Gr) andN_(RE) ^(CCE) which is the number of REs per CCE, and N_(RB) is definedas the product of N_(RB) ^(Gr) and N_(Gr), thereby implementing mappingof the transmission mode.

FIGS. 32 and 33 illustrate, in a stepwise manner, example operations ofa block interleaver constructed according to an embodiment of theinvention.

Specifically, FIG. 32 illustrates an input process and an intra-columnshift operation of the block interleaver and FIG. 33 illustrates aninter-column permutation operation, an inter-row permutation operation,and an output process of the block interleaver.

The block interleaver operations will now be described with reference toFIGS. 32 and 33. At step 1, CCEs used for a total control channel aresequentially input to the block interleaver in a row direction and, atstep 2, an intra-column shift operation is performed in units of N_(RB)^(Gr) rows in order to distribute modulated symbols in each CCE overN_(RB) ^(Gr) resource blocks in a corresponding group for each CCE. Inan embodiment of step 2, a shift offset of each column can be determinedas expressed in the following Mathematical Expression 24.

D _(offset)=(c·k)% N _(RB) ^(Gr) ,c=0,1, . . . ,N _(RB)−1  [MATHEMATICALEXPRESSION 24]

In Mathematical Expression 24, k is an integer value that defines acolumn-based shift offset.

At step 3, inter-column permutation is performed in order to distributeCCEs in a resource block. A permutation pattern used in this process mayuse a previously suggested scheme or a scheme defined to be optimizedfor the number of columns “N_(bit) ^(RB)”.

Additional benefit can be expected if this operation is applied to thecase where the frequency band of the resource block is larger than acoherent bandwidth of frequency selective fading when allocation is madeto subcarriers in units of resource blocks in a frequency region.

In addition, randomization of inter-cell interference can be implementedas an operation for shifting by a fixed value uniquely generated foreach cell through a cell ID or a combination of a cell ID and a cellgroup ID.

In an alternative method, randomization of inter-cell interference canbe implemented as an operation of shifting uniquely in each row byapplying values generated by a random generation function obtained froma cell ID and a cell group ID to each subframe unit in the time domainor each row unit corresponding to a resource block in the frequencydomain or both the units in the time-frequency domain.

At step 4, it is possible to implement a function to locate resourceblocks so as to achieve frequency diversity in a total systemtransmission band and a function to apply coordination of inter-cellinterference by assigning a cell-specific offset to each cell. Eachfunction can be represented by the following Mathematical Expression 25.

Input(r,c)r=0,1, . . . ,N _(RB)−1

c=0,1, . . . ,N _(RB) ^(bit)−1

Output(r′,c)r′=(s(r,M)+t(cell_ID))mod N _(RB)  [MATHEMATICAL EXPRESSION25]

In Mathematical Expression 25, M is a value representing the distancebetween resource blocks of the same group in a system transmission band,and s(r, M) can be represented by the following Mathematical Expression26.

s(r,M)=└r/N _(RB) ^(Gr) ┘+M·(r % N _(RB) ^(Gr))  [MATHEMATICALEXPRESSION 26]

Here, s(r,M) can be represented by the following Mathematical Expression27 when M is defined as the number of groups “N_(Gr)” set in the band.Here, N_(Gr) may be a value obtained by dividing the total number ofresource blocks “N_(RB) ^(Gr)” used in a transmission band by the numberof resource blocks “N_(RB)” per group.

s(r,M)=└r/N _(RB) ^(Gr) ┘+N _(Gr)·(r % N _(RB) ^(Gr))=└r/N _(RB)^(Gr)┘+(N _(RB) /N _(RB) ^(Gr))·(r % N _(RB) ^(Gr))  [MATHEMATICALEXPRESSION 27]

When it is assumed that “M” is equal to or greater than the number ofcells “R” in a base station, a function t(cell_ID) that serves ascoordination of inter-cell interference is basically defined asexpressed in the following Mathematical Expression 28.

t(cell_ID)=cell_ID,cell_ID=0,1, . . . ,R−1  [MATHEMATICAL EXPRESSION 28]

At the final step 5, modulated symbols are sequentially read and outputfrom the block interleaver in a row direction and modulated symbolscorresponding respectively to elements of each row are mapped to REs ofeach resource block.

FIG. 34 is a flow diagram sequentially illustrating CCE-to-RE mappingprocesses according to an embodiment of the invention.

Specifically, FIG. 34 illustrates CCEs and changes in the positions ofmodulated symbols in the CCEs when an interleaving operation has beenperformed at each step in the case where a block interleaving operationis implemented in a cell A according to the 5 steps described above withreference to FIGS. 31 to 33. A bottom portion of FIG. 34 illustratesCCEs and changes in the positions of modulated symbols in the CCEs whenan interleaving operation has been performed using a different shiftoffset and permutation pattern different from those of the cell A in thecase where a block interleaving operation is implemented in another cell(i.e., cell B) according to the 5 steps described above with referenceto FIGS. 31 to 33.

Embodiment 7

In this embodiment, when an arbitrary one of a variety of downlinkcontrol channels is transmitted through one or more OFDM symbols,interleaving can be performed on modulated symbols or mini-CCEs includedin a CCE of the arbitrary control channel transmitted through each OFDMsymbol. Specifically, modulated symbols or mini-CCEs of CCEs are dividedinto n groups so that the modulated symbols or mini-CCEs can betransmitted through n OFDM symbols and interleaving is performed onmodulated symbols or mini-CCEs of CCEs transmitted through the same OFDMsymbol, taking into consideration the respective OFDM symbols to whichthe groups are mapped.

Although the following description is limited to mapping of mini-CCEs,it will be apparent that the same method can be applied to mapping ofmodulated symbols.

FIG. 35 illustrates an example method for performing mapping afterinterleaving is done for each OFDM symbol according to an embodiment ofthe invention.

Specifically, FIG. 35 illustrates an example procedure in which CCEs,which are unit elements of a control channel, are combined to performinterleaving and are then mapped to one or more OFDM symbols.Especially, it can be seen from FIG. 35 that interleaving is performedon mini-CCEs in CCEs transmitted through the same OFDM symbols.

First, a control channel includes one or more CCEs, and each CCE isdivided into one or more sub-blocks at step S200. In the case where thecontrol channel is transmitted through one or more symbols, this processserves to distribute and transmit each CCE over the OFDM symbolscarrying the control channel, thereby increasing diversity gain andmaking power of each symbol as uniform as possible.

In the example of FIG. 35, each of the CCEs (CCE 1 (21), CCE 2 (22), andCCE 3 (23)) is divided into three sub-blocks in the case where thenumber of OFDM symbols carrying a control channel is 3. Here, the sizeof each CCE sub-block size, i.e., the number of mini-CCEs included ineach sub-block, is determined according to a ratio of the number ofphysical resource element groups that can be used for transmission of aspecific control channel(s) or all control channels among remainingresource elements, other than resource elements used for a specificsignal or channel such as a reference signal, to the total number ofresource elements that can be used for each OFDM symbol.

In this case, mini-CCEs included in the first sub-block of each CCE aretransmitted through the first OFDM symbol 27, mini-CCEs included in thesecond sub-block of each CCE are transmitted through the second OFDMsymbol 28, and mini-CCEs included in the third sub-block of each CCE aretransmitted through the third OFDM symbol 29.

First, when N_(i) ^(RE) is the number of available physical resourceelements in an ith OFDM symbol, the number N_(i) ^(REG) of availableresource element groups in the ith OFDM symbol can be represented by thefollowing Mathematical Expression 29.

                [MATHEMATICAL  EXPRESSION  29]${N_{i}^{REG} = \left\lfloor \frac{N_{i}^{RE}}{k} \right\rfloor},{i = 0},\ldots \mspace{14mu},{n - 1}$

In Mathematical Expression 29, k is a variable indicating the number ofresource elements used in one mini-CCE. This variable is used when amultiple antenna transmit diversity scheme is applied as describedabove.

In Mathematical Expression 29, the number N_(i) ^(REG) of availableresource element groups can be determined excluding the number ofresource element groups used for transmission of all or part of channelssuch as a PCFICH, a PHICH, and a PICH and a reference signal in the ithOFDM symbol.

The following Mathematical Expression 30 represents an example methodfor determining the number of mini-CCEs M_(i) included in each sub-blockwhen each CCE is divided into sub-blocks.

                [MATHEMATICAL  EXPRESSION  30]${M_{i} = \left\lfloor {N_{{\min \; i} - {CCE}}^{CCE} \cdot \frac{N_{i}^{REG}}{\sum\limits_{i = 0}^{n - 1}\; N_{i}^{REG}}} \right\rfloor},{i = 0},\ldots \mspace{14mu},{n - 1}$

Mathematical Expression 30 represents a method for determining thenumber of mini-CCEs M_(i) included in each sub-block by multiplying thetotal number of mini-CCEs N_(min i-CCE) ^(CCE) included in one CCE bythe ratio of the number of available resource element groups N_(i)^(REG) in the ith OFDM symbol to the number of available resourceelement groups

$\sum\limits_{i = 0}^{n - 1}\; N_{i}^{REG}$

in the OFDM symbols carrying the control channel.

If the number of mini-CCEs M_(i) included in each sub-block isdetermined using the method of Mathematical Expression 30, it ispossible to more efficiently perform the method for performinginterleaving for each mini-CCE transmitted through the OFDM symbolsaccording to this embodiment since the size of each sub-block isdetermined using the ratio of the number of available resource elementgroups for each OFDM symbol.

If the size of each sub-block is determined in this manner, aninterleaving set is constructed from each CCE by combining sub-blocks ofeach OFDM symbol. Here, the interleaving set is a unit for interleaving.An interleaving set 24 associated with the first OFDM symbol, aninterleaving set 25 associated with the second OFDM symbol, and aninterleaving set 26 associated with the third OFDM symbol areillustrated in FIG. 35.

Then, at step S220, interleaving is performed on each interleaving set.That is, interleaving is performed for each OFDM symbol. Here,interleaving may be performed using a cell-specific pattern or acell-common pattern in multi-cell environments. When interleaving isperformed using a cell-common pattern, a random pattern can be used toreduce inter-cell interference or a specific permutation pattern or anarbitrary permutation pattern can be used to reduce inter-cellinterference. It is also possible to use a method of performing shiftingusing a cell-specific value based on cell-specific information such as acell ID.

A block interleaver can be used to perform interleaving at step S220.Interleaving can be performed for each row or column of the blockinterleaver. A random pattern or a specific permutation pattern can beused as the interleaving pattern as described above. Details of theconfiguration and operation of the block interleaver will be describedbelow with reference to FIG. 35.

After interleaving is performed in this manner, mini-CCEs interleavedfor each of the first, second, and third OFDM symbols 27, 28, and 29 aremapped to resource element groups in the corresponding OFDM symbol andare then transmitted through the mapped resource element groups at stepS230.

The number of mini-CCEs allocated to each individual OFDM symbol of eachcontrol channel can be set to be different according to an index of eachCCE or control channel so as to support as many control channels or asmany as CCEs required to transmit control channels in a subframe aspossible.

For example, the number of mini-CCEs can be set to be differentaccording to whether the index of the control channel or CCE is even orodd. Alternatively, the number of mini-CCEs for indices set in aspecific period among total indices can be set to be different from thenumber of mini-CCEs for remaining indices. In addition, some indices canbe specified and the number of mini-CCEs in an OFDM symbol for thespecified indices can be set to be different from that of remainingindices.

Reference will now be made to an example method for individuallydetermining the respective numbers of mini-CCEs allocated to each OFDMsymbol for CCEs of control channels.

The following Mathematical Expression 31 represents an example methodfor determining the number N_(i,j) ^(min i-CCE) of mini-CCEs, which aretransmitted through each ith OFDM symbol, in a jth CCE among all CCEs ofcontrol channels in a subframe.

                [MATHEMATICAL  EXPRESSION  31]${N_{i,j}^{{\min \; i} - {CCE}} = {M_{i} + {\left\lbrack {\left( {j + \left\lfloor {i/2} \right\rfloor} \right)\% \mspace{14mu} 2} \right\rbrack \cdot \left\lbrack {\left\{ {\left( {i + 1} \right) \cdot 2^{3 - n}} \right\} \% \mspace{14mu} 2} \right\rbrack}}},{i = 0},\ldots \mspace{14mu},{n - 1},{j = 0},\ldots \mspace{14mu},{{\min\limits_{{1 = 0},\ldots \mspace{14mu},{n - 1}}\left\{ \left\lfloor \frac{N_{i}^{{\min \; i} - {CCE}}}{M_{i}} \right\rfloor \right\}} - 1}$

“M_(i)” calculated in Mathematical Expression 30 can be used as thenumber of mini-CCEs M_(i) included in each sub-block in MathematicalExpression 31. As can be seen from a bottom portion of MathematicalExpression 31, an index j identifying each CCE ranges from 0 to theminimum of the respective numbers of CCEs that can be transmittedthrough the OFDM symbols.

The following Table 6 illustrates an example of N_(i,j) ^(min i-CCE)determined through the above Mathematical Expression 31 in the case ofn=3.

TABLE 6 i j 0 1 2 0 1 3 5 1 2 3 4 2 1 3 5 . . . . . . . . . . . .

If the same ratio of the numbers of mini-CCEs of sub-blocks is used as avalue of M_(i) for every CCE, the ratio of the respective numbers ofmini-CCEs of OFDM symbols will be determined to be 1:3:5 for each CCE.However, if different ratios are applied to CCEs according toMathematical Expression 31, a ratio of 2:3:4 can be applied to thesecond CCE (j=1) so that it is possible to increase the number ofmini-CCEs transmitted through the first OFDM symbol and to reduce thenumber of mini-CCEs transmitted through the third OFDM symbol as can beseen from Table 6.

According to this method, a fixed ratio is not applied as the value ofM_(i) and, instead, the respective numbers of mini-CCEs transmitted forthe OFDM symbols can be controlled flexibly within a predetermined rangeof the ratio, thereby supporting a larger number of control channels ora larger number of CCEs required to transmit control channels than whena fixed ratio is applied.

The following Mathematical Expression 32 represents another examplemethod for determining the number N_(i,j) ^(min i-CCE) of mini-CCEs,which are transmitted through each ith OFDM symbol, in a jth CCE amongall CCEs of control channels in a subframe.

                [MATHEMATICAL  EXPRESSION  32]${N_{i,j}^{{\min \; i} - {CCE}} = {M_{i} + {\left\{ {{\left\lfloor {\left( {j\mspace{14mu} \% \mspace{14mu} 3} \right)/2} \right\rfloor \cdot \left( {- 1} \right)^{i}} + i} \right\} \cdot \left\{ {1 - \left\lfloor \frac{i}{2} \right\rfloor} \right\}}}},{i = 0},\ldots \mspace{14mu},{n - 1},{j = 0},\ldots \mspace{14mu},{{\min\limits_{{1 = 0},\ldots \mspace{14mu},{n - 1}}\left\{ \left\lfloor \frac{N_{i}^{{\min \; i} - {CCE}}}{M_{i}} \right\rfloor \right\}} - 1}$

Details of Mathematical Expression 32 are similar to those ofMathematical Expression 31. The following Table 7 illustrates an exampleof N_(i,j) ^(min i-CCE) determined through the above MathematicalExpression 32 in the case of n=3.

TABLE 7 i j 0 1 2 0 2 3 4 1 2 3 4 2 3 2 4 . . . . . . . . . . . .

In the example of Table 7, a ratio of 3:2:4 can also be applied to thethird CCE (j=2) so that it is possible to increase the number ofmini-CCEs transmitted through the first OFDM symbol and to reduce thenumber of mini-CCEs transmitted through the second OFDM symbol as can beseen from Table 6.

The following Mathematical Expression 33 represents another examplemethod for determining the number N_(i,j) ^(min i-CCE) of mini-CCEs,which are transmitted through each ith OFDM symbol, in a jth CCE amongall CCEs of control channels in a subframe.

                [MATHEMATICAL  EXPRESSION  33]${N_{i,j}^{{\min \; i} - {CCE}} = {M_{i} + i}},{i = 0},\ldots \mspace{14mu},{n - 1},{j = 0},\ldots \mspace{14mu},{{\min\limits_{{1 = 0},\ldots \mspace{14mu},{n - 1}}\left\{ \left\lfloor \frac{N_{i}^{{\min \; i} - {CCE}}}{M_{i}} \right\rfloor \right\}} - 1}$

Details of Mathematical Expression 33 are similar to those ofMathematical Expression 31. The following Table 8 illustrates an exampleof N_(i,j) ^(min i-CCE) determined through the above MathematicalExpression 32 in the case of n=2.

TABLE 8 i j 0 1 0 4 5 1 4 5 2 4 5 . . . . . . . . .

The above method, in which the number of mini-CCEs allocated to eachindividual OFDM symbol of each control channel is set to be differentaccording to an index of each CCE or control channel, can be appliedwhen the number of mini-CCEs allocated to each individual OFDM symbol ofeach control channel, calculated according to a ratio of availableresource element groups of all control channels or a specific controlchannel(s) for each OFDM symbol, is not a positive integer.

The number of available resource element groups of a control channel ofinterest can be calculated excluding resource element groups carrying adifferent type of control channel from the control channel of interestas described above. In this case, if the number of OFDM symbols carryinga different type of control channel or the number of resource elementgroups for each OFDM symbol is changed, then the number of availableresource element groups for the control channel of interest can also bechanged. Accordingly, the method can also be applied to this case.

That is, when a control channel is transmitted through three OFDMsymbols, the example of Table 6 can be considered an example that can beapplied when a different type of control channel is transmitted througha first OFDM symbol and the example of Table 7 can be considered anexample that can be applied when a different type of control channel istransmitted through all the three OFDM symbols allocated for controlchannel transmission. In addition, when a control channel is transmittedthrough two OFDM symbols, the example of Table 8 can be considered anexample that can be applied when a different type of control channel istransmitted through first and second OFDM symbols.

Embodiment 8

FIG. 36 illustrates an example method for transmitting different typesof control channels according to an embodiment of the invention.

This embodiment provides a method in which, when different types ofcontrol channels are transmitted, interleaving is performed on mini-CCEsincluded in CCEs of one or more types of control channels instead ofindividually performing interleaving for each of the types of controlchannels.

As described above, downlink control channels include not only a PDCCHtransmitting control information of downlink transmission data but alsovarious types of control channels such as a PCFICH, a PHICH, and a PICHand a reference signal.

FIG. 36 illustrates an example in which a PCFICH 30, a PHICH 31, and aPDCCH 32 are transmitted as downlink control channels. Here, even thoughthe PCFICH 30 should generally be separately taken into considerationsince the position of the PCFICH 30 transmitted in the OFDM symbol ispredetermined, it is possible to take into consideration the PHICH 31and the PDCCH 32 together so that both the PHICH 31 and the PDCCH 32 canbe mapped to resource element groups of OFDM symbols and then betransmitted through the mapped resource element groups.

Here, interleaving can be performed taking into consideration the PHICH31 and the PDCCH 32 together so that both the PHICH 31 and the PDCCH 32can be mapped to resource element groups of OFDM symbols and then betransmitted through the mapped resource element groups. It will also bepossible to apply the method in which interleaving is performed on eachmini-CCE transmitted for each OFDM symbol as described above withreference to FIG. 35.

For example, an interleaving set for performing interleaving taking intoconsideration all CCEs of the PHICH 31 and the PDCCH 32 can bedetermined at step 300 and interleaving can be performed to transmitthem through one or more OFDM symbols at step S310. To determine theinterleaving set at step S300, it is possible to apply a methodidentical or similar to the method described above with reference toFIG. 35.

For use of OFDM symbols, the PHICH can be defined separately from thePDCCH. For example, even when a total of three OFDM symbols is used forPDCCH transmission, the PHICH can use only one OFDM symbol.

That is, the PHICH can be transmitted selectively using at least one ofthe OFDM symbols carrying control channels. The OFDM symbol transmittingthe PHICH can be defined as a PHICH duration, which can be divided intoa normal mode and an extended mode. For example, in the case of thenormal mode, the use of the OFDM symbols for transmitting the PHICH canbe defined such that the PHICH is transmitted using the first of theOFDM symbols carrying control channels in the case of the normal modeand the PHICH is transmitted using all the OFDM symbols carrying controlchannels in the case of the extended mode.

The following description will be given with reference to a definitionof the use of OFDM symbols for PHICH transmission such that the PHICH istransmitted using the first OFDM symbol in the case of a permutationduration of “1”, the PHICH is transmitted using the first and secondOFDM symbols in the case of a permutation duration of “2”, and the PHICHis transmitted using the first, second, and third OFDM symbols in thecase of a permutation duration of “3”.

FIGS. 37( a) to 37(c) illustrate an example method for allocatingmini-CCEs of the PHICH transmitted through each OFDM symbol wheninterleaving is performed on the PHICH for each OFDM symbol according toan embodiment of the invention.

In the example of FIGS. 37( a) to 37(c), a total of K PHICHs aretransmitted through one subframe and PHICHs are shown as three blocksunder the assumption that each PHICH extended according to a spreadingfactor of SF=4 is repeated three times. That is, since one PHICH isextended according to SF=4, it can be assumed that one block correspondsto one mini-CCE when one PHICH is mapped in units of mini-CCEs includingfour symbols.

FIG. 37( a) illustrates an example method for allocating mini-CCEs ofPHICHs transmitted through each OFDM symbol when the PHICH duration is“1.” In the case where the PHICH duration is “1,” the PHICH istransmitted only through the first OFDM symbol and therefore K PHICHsare all interleaved together during the interleaving of the first OFDMsymbol without performing separate allocation.

FIG. 37( b) illustrates an example method for allocating mini-CCEs ofPHICHs transmitted through each OFDM symbol when the PHICH duration is“2.” In the case where the PHICH duration is “2,” the PHICH istransmitted through the first and second OFDM symbols and therefore itis difficult to transmit one PHICH using two OFDM symbols uniformly inthe case where one PHICH consists of three mini-CCEs as in thisembodiment. Accordingly, in the case of this embodiment, a differentrate of use of each OFDM symbol can be applied to each PHICH so that itis possible to transmit each PHICH using two OFDM symbols uniformly whena total of K PHICHs are taken into consideration.

Specifically, two mini-CCEs of PHICH #0 can be transmitted through thefirst OFDM symbol and the remaining one mini-CCE can be transmittedthrough the second OFDM symbol. In the case of PHICH #1, one mini-CCEcan be transmitted through the first OFDM symbol and the remaining twomini-CCEs can be transmitted through the second OFDM symbol, unlike thecase of PHICH #0. Repeating this pattern will allow each PHICH to betransmitted using two OFDM symbols uniformly when a total of K PHICHsare taken into consideration.

FIG. 37( c) illustrates an example method for allocating mini-CCEs ofPHICHs transmitted through each OFDM symbol when the PHICH duration is“3.” In this case, since each PHICH consists of mini-CCEs, mini-CCEs ofeach PCFICH can be transmitted through each OFDM symbol.

Although the methods of FIGS. 37( a) to 37(c) have been described simplywith reference to examples where each PHICH consists of three mini-CCEs,the methods can be applied to any other examples. The followingMathematical Expression 34 represents an example method for determiningthe number N_(i,k) _(—) _(PHICH) ^(min i-CCE) of mini-CCEs transmittedthrough an ith OFDM symbol in a kth PHICH.

                [MATHEMATICAL  EXPRESSION  34]$N_{i,{k\_ PHICH}}^{{\min \; i} - {CCE}} = {\left\lfloor \frac{N_{PHICH}^{{\min \; i} - {CCE}}}{N_{PHICH}} \right\rfloor + {\left\{ {\left( {N_{PHICH} + 1} \right) \cdot \left( {i + k + 1} \right)} \right\} \% \mspace{14mu} 2}}$

In Mathematical Expression 34, N_(PHICH) represents a PHICH duration andN_(PHICH) ^(min i-CCE) represents the total number of mini-CCEs in eachPHICH.

When one of different types of control channels requires stablefrequency diversity, it is possible to satisfy this requirement byperforming distribution and multiplexing at an input terminal of aninterleaver before interleaving.

FIG. 38 illustrates an example method for transmitting two or moredifferent types of control channels by performing interleaving on thedifferent types of control channels together for each OFDM symbolaccording to an embodiment of the invention.

Although the method of FIG. 38 is similar to that of FIG. 35, the methodof FIG. 38 differs from that of FIG. 35 in that two different types ofcontrol channels, a PDCCH and a PHICH for ACK/NACK transmission, aretaken into consideration together. Specifically, FIG. 38 illustrates anexample where the PHICH is transmitted through only the first OFDMsymbol while the PDCCH is transmitted through three OFDM symbols. Asshown in FIG. 38, mini-CCEs in CCEs of the PHICH and the PDCCH that hasbeen determined to be transmitted through the first OFDM symbol areinput together to an interleaver 50 of the first OFDM symbol so that themini-CCEs in the PHICH and the PDCCH are interleaved together at theinterleaver 50.

FIG. 39 illustrates another example method for transmitting two or moredifferent types of control channels by performing interleaving on thedifferent types of control channels together for each OFDM symbolaccording to an embodiment of the invention.

Although the method of FIG. 39 is similar to that of the embodiment ofFIG. 35, the method of FIG. 38 differs from that of FIG. 35 in that twodifferent types of control channels, a PDCCH and a PHICH, are taken intoconsideration together. Specifically, FIG. 39 illustrates an examplewhere the PHICH is transmitted through three OFDM symbols while thePDCCH is also transmitted through the three OFDM symbols.

As shown in FIG. 39, mini-CCEs in CCEs of the PDCCH and mini-CCEs in thePHICH that has been determined to be transmitted through the first OFDMsymbol are input together to an interleaver 60 of the first OFDM symbolso that the mini-CCEs in the PHICH and the PDCCH are interleavedtogether at the interleaver 60. In addition, mini-CCEs in CCEs of thePDCCH and mini-CCEs in the PHICH determined to be transmitted throughthe second OFDM symbol are input together to an interleaver 61 of thesecond OFDM symbol so that the mini-CCEs in the PHICH and the PDCCH areinterleaved together at the interleaver 61. In addition, mini-CCEs inCCEs of the PDCCH and mini-CCEs in the PHICH determined to betransmitted through the third OFDM symbol are input together to aninterleaver 62 of the third OFDM symbol so that the mini-CCEs in thePHICH and the PDCCH are interleaved together at the interleaver 62.

In the case where two or more different types of control channels areinterleaved together as shown in FIGS. 38 and 39, resource elementgroups transmitting different types of control channels that areinterleaved together are taken into consideration as opposed to beingexcluded when the number of available resource element groups isdetermined in each OFDM symbol. In addition, as shown in FIGS. 38 and39, the resource element groups may be multiplexed in a sequentialmanner and may also be distributed and multiplexed for the sake ofoptimizing frequency domain diversity.

Reference will now be made to a method in which a block interleaver isused to perform interleaving on each OFDM symbol according to theinvention. Particularly, it is possible to use a block interleaver thatoperates with different input and output directions. The order ofelements before they are input to the block interleaver and the order ofelements that are output from the block interleaver can be changed (orcan be made different) through the simple method of using differentinput and output directions, thereby allowing channel elements to bedistributed and transmitted uniformly over resources.

A block interleaver, which performs row-wise writing (or row-directionalinput) and column-wise reading (or column-directional output), permutesrow positions of elements in each column and outputs the elements. Onthe other hand, a block interleaver, which performs column-wise writing(or column-directional input) and column-wise reading (orrow-directional output), permutes column positions of elements in eachrow and outputs the elements.

Here, permutation can be performed through reordering according to aspecific random pattern and can also be performed according to aspecific pattern. In the case where a rule is used to generate apattern, a rule may be generated and applied based on a correspondingcolumn or row index and a rule may also be generated and appliedregardless of a column or row index. To reduce inter-cell interference,it is possible to generate a cyclically shifted version of the permutedpattern using cell-specific information such as a cell ID.

According to this embodiment, it is possible to implement respectiveinterleavers of OFDM symbols used for control channel transmission toperform interleaving for each OFDM symbol. When the configuration of theinterleaver of each of the OFDM symbols is defined by the number of rowsand the number of columns, the number of rows and the number of columnsof each symbol interleaver can be set to be equal and can also be set tobe different for given purposes.

Reference will now be made to the configuration and operation of a blockinterleaver which performs row-wise writing (or row-directional input)and column-wise reading (or column-directional output). Similar detailedoperations can be applied to a block interleaver which performscolumn-wise writing (or column-directional input) and column-wisereading (or row-directional output), with the only difference being rowor column directions.

The number of columns of the block interleaver of each OFDM symbol canbe defined in association with the number of mini-CCEs, allocated to theOFDM symbol, of all control channels or CCEs. Of course, the number ofcolumns can also be defined using a given rule for a given purpose. Inone method for defining the number of rows, first, a basic row size canbe set based on the total number of mini-CCEs input to the blockinterleaver and a different row size from the basic row size can be setbased on a preset rule of reordering or permutation of each column.

In the case where interleaving is performed on different types ofcontrol channels, the method for performing intra-column permutation andthe method for setting the number of rows and the number of columnstaking into consideration characteristics and requirements of a specificchannel can be used for each type of control channel by setting aspecific value and pattern based on the purposes described above.

The following Mathematical Expression 35 represents an example methodfor determining the number C_(i) of columns of an interleaver of eachOFDM symbol when interleaving is applied only to a PDCCH and thefollowing Mathematical Expression 36 represents an example method fordetermining the number C_(i) of columns of an interleaver of each OFDMsymbol when a PDCCH and a PHICH are interleaved together.

               [MATHEMATICAL  EXPRESSION  35]$C_{i} = {\max\limits_{{all}\mspace{14mu} j}{\left\{ N_{i,j}^{{\min \; i} - {CCE}} \right\} \mspace{256mu}\left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 36} \right\rbrack}}$$C_{i} = {\max\limits_{{{all}\mspace{14mu} j},k}\left\{ {N_{i,j}^{{\min \; i} - {CCE}},N_{i,{k\_ PHICH}}^{{\min \; i} - {CCE}}} \right\}}$

N_(i,j) ^(min i-CCE) in Mathematical Expressions 35 and 36 representsthe number of mini-CCEs of a jth CCE transmitted through an ith OFDMsymbol and N_(i,j) _(—) _(PHICH) ^(min i-CCE) in

Mathematical Expression 36 represents the number of mini-CCEs of a kthPHICH transmitted through the ith OFDM symbol.

The following Mathematical Expression 37 represents an example methodfor determining the number R_(i) of rows of an interleaver of each OFDMsymbol when interleaving is applied only to a PDCCH and the followingMathematical Expression 38 represents an example method for determiningthe number R_(i) of rows of an interleaver of each OFDM symbol when aPDCCH and a PHICH are interleaved together.

                [MATHEMATICAL  EXPRESSION  37]$R_{i} = {\left\lceil \frac{N_{i}^{{\min \; i} - {CCE}}}{C_{i}} \right\rceil \mspace{256mu}\left\lbrack {{MATHEMATICAL}\mspace{14mu} {EXPRESSION}\mspace{14mu} 38} \right\rbrack}$$R_{i} = \left\lceil \frac{N_{i}^{{\min \; i} - {CCE}} + N_{PHICH\_ i}^{{\min \; i} - {CCE}}}{C_{i}} \right\rceil$

N_(i) ^(min i-CCE) in Mathematical Expressions 37 and 38 represents thenumber of mini-CCEs of a PDCCH transmitted through an ith OFDM symboland N_(PHICH) _(—i) ^(min i-CCE) in Mathematical Expression 38represents the number of mini-CCEs of a PHICH transmitted through theith OFDM symbol. Here, N_(PHICH) _(—i) ^(min i-CCE) can be determined asin the following Mathematical Expression 39.

                [MATHEMATICAL  EXPRESSION  39]$N_{PHICH\_ i}^{{\min \; i} - {CCE}} = {\left\lceil \frac{N_{UL\_ VRB}}{SF} \right\rceil \cdot {RPF}}$

SF in Mathematical Expression 39 represents a spreading factor, RPFrepresents the number of repetitions of the PHICH, and N_(UL) _(—)_(VRB) represents the number of uplink resource blocks (UL VRBs)allocated to a system bandwidth. The value of N_(UL) _(—) _(VRB) canvary according to the system bandwidth.

The positions of resources through which a downlink PHICH is transmittedcan be determined according to downlink resource blocks through whicheach terminal transmits data. For example, in the case where the systembandwidth is 5 MHz, the number of uplink resource blocks is 25 and themaximum value “25” can be set as N_(UL) _(—) _(VRB) since the downlinkPHICH needs to indicate any resource block through which data has beentransmitted. That is, since N_(UL) _(—) _(VRB) can vary according to thesystem bandwidth, the number of mini-CCEs of a PHICH transmitted throughthe ith OFDM symbol can be determined using N_(UL) _(—) _(VRB) as avariable as in Mathematical Expression 39.

When interleaving is performed on different types of control channelsusing a symbol interleaver of the block interleaver, interleaving can beimplemented using a method in which specific control channels are fixedto specific positions (or specific row/column indices) in theinterleaver or a method in which, when a symbol sequence is input to theinterleaver, the order of symbols of the input symbol sequence ischanged according to an arbitrary method in order to accomplish thepurposes described above.

FIG. 40 illustrates an example method for performing interleaving foreach OFDM symbol using a block interleaver according to an embodiment ofthe invention.

In the case where respective mini-CCEs that are to be mapped to OFDMsymbols are distinguished before interleaving, a column reordering orpermutation pattern for an individual block interleaver to be applied toeach OFDM symbol can be defined by dividing a block interleaver 70 thatis virtually provided for all OFDM symbols into groups of columns toapply an individual block interleaver to each OFDM symbol. Here, thecolumn reordering or permutation pattern can be defined as a randompattern as described above and can also be defined as a patternaccording to a specific rule.

The following Mathematical Expression 40 represents an example methodfor defining the number C of columns when respective block interleaversof OFDM symbols are regarded as one block interleaver 70.

                [MATHEMATICAL  EXPRESSION  40]$C = {\sum\limits_{i = 1}^{n}\; C_{i}}$

As can be seen from Mathematical Expression 40, the number of columns Ccan be represented by the sum of the respective numbers of columns ofOFDM symbols calculated through Mathematical Expression 35 or 36.

As shown in FIG. 40, in the case where control channels are transmittedthrough three OFDM symbols, the numbers of columns of respective blockinterleavers 71, 72, and 73 of the OFDM symbols can be defined as C1,C2, and C3. The respective numbers of columns of the block interleaversof the OFDM symbols can be set according to a ratio of the numbers ofphysical mini-CCEs that can be used to transmit control channels for theOFDM symbols. Of course, the respective numbers of columns of the blockinterleavers can be set to other values for other purposes. For example,“C” of the virtual block interleaver in FIG. 40 can be determined to bethe number of mini-CCEs of an arbitrary CCE and the values of “C1”,“C2”, and “C3” can be set according to the ratio of available mini-CCEsin the OFDM symbols and the requirement that C=C1+C2+C3.

In addition, the numbers of rows of the block interleavers appliedrespectively to the OFDM symbols can be defined to be different when anarbitrary one of different types of control channels is mapped only to aspecific OFDM symbol and can be alternatively defined to be equal byapplying pruning. mini-CCEs not used in individual OFDM symbols can beincorporated into corresponding block interleavers so that they areinterleaved by the block interleavers, and the values of R1, R2, and R3can be determined taking into consideration the interleaving of suchmini-CCEs.

FIG. 41 illustrates an example method in which two or more controlchannels are interleaved together and are then multiplexed andtransmitted according to an embodiment of the invention.

Specifically, FIG. 41 illustrates an example where two control channels,a PDCCH and a PHICH, are interleaved together. As shown in FIG. 41,divided interleavers can be constructed according to the same method asdescribed above with reference to FIG. 40. When an input sequence of aPHICH to a block interleaver is constructed, mini-CCEs of a PHICH can bedefined according to the characteristics of the block interleaver inorder to optimize frequency diversity.

As shown in FIG. 41, each of a plurality of PHICHs including PHICH #i,PHICH #j, and PHICH #k is transmitted by repeating a mini-CCE, whichcorresponds to a symbol extended with a spreading factor of SF=4, 3times in the frequency axis. First symbol mini-CCEs 80, 83, and 86,second mini-CCEs 81, 84, and 87, and third mini-CCEs 82, 85, and 88 ofthe PHICHs are sequentially input (or written) to a first row 89 of ablock interleaver. Thus, the three mini-CCEs of each PHICH can beinterleaved in different block interleavers. Accordingly, the method canobtain effects of uniform distribution and multiplexing over a specificor entire range of column indices.

The following Mathematical Expression 41 represents an example methodfor column-wise permutation or reordering of a block interleaver of anith OFDM symbol in an interleaving operation of a block interleaverconstructed using the above method.

(r′,c′)={(r*(1+c)+c+P}% R″,c),  [MATHEMATICAL EXPRESSION 41]

where R=0, 1, . . . , R″−1

c=0, 1, . . . , Ci−1

i=1, . . . , n(≦3)

P=R″−R′

Specifically, Mathematical Expression 41 represents an example wherethree block interleavers, which are constructed with respective sizes ofR″×C1, R″×C2, and R″×C3, are applied to three OFDM symbols,respectively, as shown in FIG. 40. Here, the same number of rows R″ isapplied to each block interleaver. In Mathematical Expression 41, C1,C2, and C3 may be equal to or different from each other when a blockinterleaver is individually applied to each OFDM symbol. Some of thevariables may have a different value and the value of each variable maymatch the number of columns of the interleaver of each individual OFDMsymbol and may also be defined based on a specific pattern or a randomvalue.

A value used in association with each column of an OFDM symbolinterleaver in Mathematical Expression 41 represents a column index thatis increased by 1 every column. However, a value not associated with thecolumn index can also be applied to each column.

In the case where a block interleaver operates using a specific functionto perform interleaving, it may be preferable that the number R of rowsof the block interleaver be set to a prime number. When the determinedvalue (R′) of R is a prime number, it can be immediately determined tobe the number of rows R (R″) of the block interleaver.

When the determined value (R′) of R is not a prime number, the smallestprime number greater than the value R determined above can be determinedto be the number of rows R (R″) of the block interleaver. That is, “P”in Mathematical Expression 41 represents the difference between thefinally determined value (R″) of R in the case where the number of rowsof the block interleaver is determined to be a prime number and thevalue (R′) of R determined without taking into consideration primeness.

On the other hand, different offsets can be allocated to column indicesof respective block interleavers of OFDM symbols so that mini-CCEs ofCCEs are input in a distributed manner to the block interleavers of theOFDM symbols and mini-CCEs are also distributed over all OFDM symbolswhen interleaving is performed for each OFDM symbol in order to reliablyprovide frequency domain diversity to CCEs.

The following Mathematical Expression 42 represents an example methodfor allocating different offsets to column indices of respective blockinterleavers of OFDM symbols.

(r′,c′)={(r*(1+c _(—) i+P)+c _(—) i+P}% R″,c),  [MATHEMATICAL EXPRESSION41]

where R=0, 1, . . . , R″−1

c=0, 1, . . . , Ci−1

i=1, . . . , n(≦3)

P=R″−R′

In the example of Mathematical Expression 42, three block interleaversare constructed respectively for three OFDM symbols. In this example,when a column index of a block interleaver of each OFDM symbol isdefined as “c,” an index value of each column of the block interleaverof the first OFDM symbol is equal to a value of the index “c”corresponding to the column. An index value of each column of the blockinterleaver of the second OFDM symbol is defined as the sum of a valueof the index “c” corresponding to the column and the number “C1” ofcolumns of the block interleaver of the first OFDM symbol so that thecolumn index values of the block interleaver of the second OFDM symbolare set to continue from those of the block interleaver of the secondOFDM symbol. The index values of columns of the block interleaver of thethird OFDM symbol are set in the same manner.

In this manner, different offsets are allocated to column indices of therespective block interleavers of OFDM symbols so that mini-CCEs aredistributed over all OFDM symbols, thereby reliably providing frequencydomain diversity to CCEs.

In the above method for mapping virtual resources to physical resourcesand using block interleaving, an interleaver can be commonly used formultiple cells while mapping can be performed taking into considerationcell-specific information, for example a cell identifier (ID), in orderto minimize inter-cell interference in multi-cell environments.

As described above, interleaver elements can be output from theinterleaver after the elements are cyclically shifted usingcell-specific information such as a cell ID for each cell after a blockinterleaving process is completed. In addition, when outputs of theinterleaver are mapped to physical resources, the interleaver elementscyclically shifted using cell-specific information such as a cell ID foreach cell can also be mapped to physical resources.

For example, for a cell having a shift factor of “0”, an output sequenceof an interleaver can be directly mapped to physical resource elementswithout shifting a random pattern generated using the interleaver and,for a cell having a shift factor of “10”, the output sequence of theinterleaver can be mapped to physical resource elements after cyclicallyshifting elements in a random pattern in the interleaver output sequenceby 10. That is, a cyclic shift method is applied such that elementsinterleaved on a column basis are mapped to physical resources after acyclic shift is applied to an interleaving pattern of all elements ofthe interleaver using information such as a cell ID for each cell,unlike the previously described method.

The invention may also provide a method in which, before all mini-CCEsof CCEs used for control channel transmission are input to theinterleaver, the mini-CCEs are divided according to OFDM symbols usedfor control channel transmission and interleaving common to acorresponding cell is performed on mini-CCEs that are to be mapped toresource element groups of each OFDM symbol. Here, a mini-CCE sequenceinput to the block interleaver may be constructed in a format in whichvarious control channels are multiplexed.

Mathematical Expression 43 represents an example method of representingan algorithm that can implement virtual interleaving for an interleavingoperation using the block interleaver described above.

                           [Mathematical  Expression  43]  k = (j)%  C_(i)$s_{j}^{i} = {\left\lbrack {\left\{ {{\left\lfloor \frac{j}{C_{i}} \right\rfloor \cdot \left\{ {1 + \left( {k + {\sum\limits_{m = 0}^{i}\; C_{m}} - C_{i}} \right)} \right\}} + \left( {k + {\sum\limits_{i = m}^{0}\; C_{m}} - C_{i}} \right) + P_{i}} \right\} \% \mspace{14mu} R_{i}^{l}} \right\rbrack + {k \cdot R_{i}^{l}}}$  where, j = 0, 1, …  , (R_(i)^(l) ⋅ C_(i) − 1)

In Mathematical Expression 43, S_(j) ^(i) represents an output positionindex of a mini-CCE corresponding to an input position index j at an ithOFDM symbol interleaver. This value may represent a position index in ablock interleaver allocated for virtual interleaving. In addition,values calculated using the same method as those used when an individualblock interleaver of each ith OFDM symbol is implemented can be used asR_(i) ^(j), C_(i), and P_(i).

The above embodiments of the present disclosure have been describedfocusing on the data communication relationship between a terminal (UE)and a base station. The base station is a terminal node in a networkwhich performs communication directly with the terminal. Specificoperations which have been described as being performed by the basestation may also be performed by upper nodes as needed. That is, it willbe apparent to those skilled in the art that the base station or anyother network node may perform various operations for communication withterminals in a network including a number of network nodes. The term“base station” may be replaced with another term such as “fixedstation”, “Node B”, “eNode B (eNB)”, or “access point”. The term“terminal” may also be replaced with another term such as “userequipment (UE)”, “mobile station (MS)”, or “mobile subscriber station(MSS)”.

Those skilled in the art will appreciate that the present invention maybe embodied in other specific forms than those set forth herein withoutdeparting from the spirit and essential characteristics of the presentinvention. The above description is therefore to be construed in allaspects as illustrative and not restrictive. The scope of the inventionshould be determined by reasonable interpretation of the appended claimsand all changes coming within the equivalency range of the invention areintended to be embraced in the scope of the invention.

INDUSTRIAL APPLICABILITY

The present invention relates to a method for transmitting controlchannels to one or more mobile terminals in a mobile communicationsystem and provides a method for distributing, when a control channel istransmitted, modulated control channel symbols uniformly overtransmission resources by additionally performing interleaving using ablock interleaver to transmit the modulated control channels through thetransmission resources. The invention can also reduce inter-cellinterference by performing shifting using a cell-specific factor. Theinvention is not necessarily applied to a specific system and can beapplied to base stations, relay stations, terminals, etc., of variouswireless communication systems according to standards including 3GPPLTE, IEEE 802.16e, and IEEE 802.16m and various other standardscompatible with these standards.

1-10. (canceled)
 11. A method for transmitting a physical downlinkcontrol channel (PDCCH) in a mobile communication system, the methodcomprising: inputting one or more symbol groups to a block interleaver;outputting permuted symbol groups from the block interleaver; mappingthe outputted symbol groups to resource elements allocated fortransmitting at least one PDCCH in a subframe; and transmitting the atleast one PDCCH, wherein the outputted symbol groups are cyclicallyshifted using a cell identifier.
 12. The method according to claim 11,wherein the one or more symbol groups are written to the blockinterleaver in a row direction, and the one or more permuted symbolgroups are read from the block interleaver in a column direction. 13.The method according to claim 11, wherein the performed symbol groups ispermuted by using a specific permutation pattern.
 14. The methodaccording to claim 11, wherein a size of the block interleaver isdetermined according to a number of the cyclically shifted symbol groupstransmitted in the subframe.
 15. The method according to claim 14,wherein a number of rows of the block interleaver is determined based ona predetermined number of columns of the block interleaver and thenumber of the cyclically shifted symbol groups transmitted in thesubframe.
 16. A apparatus for transmitting a physical downlink controlchannel (PDCCH) in a mobile communication system, the apparatuscomprising: a block interleaver; and one or more transmission antennas;wherein the apparatus is configured to: input one or more symbol groupsto the block interleaver; output permuted symbol groups from the blockinterleaver; map the outputted symbol groups to resource elementsallocated for transmitting at least one PDCCH in a subframe; andtransmit the at least one PDCCH by using the one or more transmissionantennas, and wherein the outputted symbol groups are cyclically shiftedusing a cell identifier.
 17. The apparatus according to claim 16,wherein the one or more symbol groups are written to the blockinterleaver in a row direction, and the one or more permuted symbolgroups are read from the block interleaver in a column direction. 18.The apparatus according to claim 16, wherein the performed symbol groupsis permuted by using a specific permutation pattern.
 19. The apparatusaccording to claim 16, wherein a size of the block interleaver isdetermined according to a number of the cyclically shifted symbol groupstransmitted in the subframe.
 20. The apparatus according to claim 19,wherein a number of rows of the block interleaver is determined based ona predetermined number of columns of the block interleaver and thenumber of the cyclically shifted symbol groups transmitted in thesubframe.